Last Friday I ventured north to Nottingham, along with Ed Parsons, Steven Feldman and Muki Haklay to attend the one day Supporting the Contextual Footprint event run by the Horizon Digital Economy Research institute at the University of Nottingham. Along the way I discovered a manner of tracking my journey that I'd hadn't previously considered, but that's covered in a previous blog post.

The focus of the Horizon event was to discuss the infrastructure needed to support location in its role as a key context and to identify any research theme that came out of the discussions; a classic case of the ill defined and fuzzy interface between the commercial world and that of academia.

Whenever I talk about the privacy implications inherent in sharing your location with an app or service, I keep coming back to the idea that it's essential to be your own source of truth for your location. This is a slightly verbose way of saying that you need to be able to lie about your location or that you need to be able to say "no, I really am here" despite what other location contexts such as GPS, cell tower triangulation or public wifi MAC address triangulation may have to say on the matter.

Of course, it's never quite as straightforward as that and here's why. The two location based mobile services that are getting a lot of coverage at the moment are FourSquare and Gowalla.

We all suffer from SPAM, the unwanted and unsolicited commercial bulk emails that are the reason we have Junk Mail filters and folders in our email clients and servers. A quick glance at the Junk folder for my personal email account shows over 300 of these since the beginning of February alone. If you use some form of instant messenger, be it MSN, Yahoo!, ICQ, AOL or any of the others on the market, you've probably come across SPIM, Instant Messaging SPAM. Then there's also mobile phone SPAM via text messages, comment SPAM, the list goes on and on.

We're poised to start seeing a new form of SPAM raise its ugly head. Let's call it LAMB for now, Location Based Advertising SPAM.

As Ed Parsons pointed out on his blog yesterday, Apple are banning location based advertising in apps. "If you build your application with features based on a user’s location, make sure these features provide beneficial information. If your app uses location-based information primarily to enable mobile advertisers to deliver targeted ads based on a user’s location, your app will be returned to you by the App Store Review Team for modification before it can be posted to the App Store."

This is a good first step in locking down potential abuses of a technology before it has a chance to get out of control. The reason we have SPAM and all the other variants in the first place is that the underlying technologies were designed in an open manner with no control mechanisms in place to thwart unsolicited and unwanted messages and content. But we need to go further than this.

One of the things I write about a lot on this blog are the areas of location and online, or digital, identity and how these two areas overlap and sometimes conflict.

I write about this stuff not only because I'm lucky enough to work in both of these areas but I also find them fascinating, compelling and nowhere is this more evident in how individuals and organisations views this arena.

Companies, if they're foresighted enough, are making major plays in the location field, fuelled by the proliferation of location aware devices (cameras, phones, netbooks and the like) and by the convergence of these devices (I use an iPhone ... is it a phone, a camera, a GPS unit, an internet terminal, a computer or some combination of them all?). There's much value to a company in knowing your customer's location and how it changes over time. Indeed it's a truism that it's much less about where you are now and much more about where you've been.

Individuals, if they're informed enough, know about the plays the companies are making in the location field and  should know how to determine the value proposition that is offered when they give up their location.

Telematics, the use of GPS and mobile technology within the automotive business, and the Web 2.0, neo and paleo aspects of location have traditionally carved parallel paths, always looking at if they would converge but somehow never quite making enough contact to cross over.

But not any more.The combination of 3G mobile communications and GPS enabled smart-phones such as the iPhone and the BlackBerry means that one way or another, the Internet and the Web are coming into the car, either in your pocket or into the car itself.

We all produce lots of online content these days; photos, videos, blogs, microblogs, status updates, Tweets, that sort of thing. Most of the pictures I produce go up on my Flickr account and there's a lot of photos, almost 3.5 thousand at the last count. Most of these almost 3.5 thousand photos are of my family, my wife, my children and last year I changed my default upload model from "anyone can see this" to "only friends and family can see this" and I went back and changed permissions on those photos I'd uploaded. On all of them. Or so I thought.

I'm writing this in my hotel room in New York, where I've been taking part in Yahoo's Open Hack NYC event and I've been taking a lot of photos which I've been posting to Flickr. Some people seem to like these photos and favourite them; each time this happens I get a nice friendly mail from Flickr telling me this. So this morning I went and looked at all the photos of mine that had been added as a favourite and I didn't like what I found. There was a photo taken last year while on holiday; a photo of one of my children, a photo which I thought was "friends and family only".

"I'm just a face in the crowd, Nothing to worry about, Not even tryin' to stand out, And I have nothing to say, It's all been taken away, I just behave and obey"

Trent Reznor, Nine Inch Nails, Getting Smaller

Ten years ago our online identity, if we had one at all, was a simple affair to manage, comprising of an email address and perhaps an avatar name or two. Fast forward to the close of the first decade of the 21st century and it's an altogether more complex affair. You've probably got several email addresses, possibly some domain names and then there's the plethora of social networking sites that you frequent, Twitter, Facebook, LinkedIn, Bebo, MySpace and so on. All of which define the online version of "you" in much the same way as your passport, driving licence and bank account defines the offline "you".

The key difference is that the online version of "you" is much more subtle, complex and diffuse. We leave scraps of our path through the internet behind us. At the Being Digital conference in London earlier this year, I tried to explain this with the clumsy phrase "digital dandruff"; in the soon to be published book, "My Digital Footprint", Tony Fish far more elegiacally describes it as our digital footprint, which is "the digital 'cookie crumbs' that we all leave when we use the some form of digital service, application, appliance, object or device, or in some cases as we pass through or by".

Managing our digital identity through those sources we know about is a challenge for a significant percentage of the online population. But despite being a challenge, it's one which is achieveable if you're willing to put enough time and effort into it. But most of us don't have the time or are unwilling to put in the effort, so our digital cookie crumbs and the varying online versions of "us" stay online, ready for someone with the time and effort to search for, find and put together with profit in mind.

Some people take an active role in managing their digital footprint and try to exploit it. Some people also try to exploit other people's digital footprint. Let's look at a concrete example of this.