Location-based social network Brightkite announced this morning that it has added what it calls the first mobile Augmented Reality advertising for U.S. markets to its AR layer in the Layar augmented reality browser. Augmented Reality (AR) is a class of technologies that place data from the web on top of a camera view of the physical world. Layar is a browser for a wide variety of AR data layers, from real-estate listings to government data to messages posted to networks like Brightkite. It is available for Android phones and was available on the iPhone until it was withdrawn from the marketplace last week due to excessive crashes.

The Brightkite ads appear to be just for electronics retailer BestBuy so far, and are displayed as unique markers in your field of view when pointed towards one of the stores.

Big round circles have been added to Brightkite camera-view annotations, designating the location of nearby BestBuy stores. The circles join the clearly different annotations for text messages and photos posted by nearby users. The ads are relatively unobtrusive for now.

These ads appear in all search results pages, whether they are relevant or not. For example, no one has posted on Brightkite about "pizza" within miles of me for the last three days, but a search for pizza displays a number of search results on my phone's radar. It turns out those are the BestBuys in my area. The same results appear in searches for "love" and "flatulence" - it's all BestBuy. If advertising proliferates on platforms like this then it's going to have to become contextual.

These are the early days in mobile Augmented Reality advertising, but the field is expected to be big. AR has been become increasingly common in recent months as a gimmick in print ads that can be held up to a webcam to display a 3D image, but we're unaware of previous experiments like what Brightkite is doing on Layar.

Is the advertising industry excited about mobile AR advertising? Blake Robinson, director of research and measurement at social media marketing firm Attention, says he is. "If the question is whether or not money will be pumped into mobile AR advertising," he says,"I'd say it's not a question of if, but when - and I'd say soon.

"For the first time in a long time local businesses could be given opportunities by advertisers to reach not just potential patrons but people who are literally at their doorsteps. There is a lot of potential for good here, a lot of potential for irritation too, but I'm more excited than daunted."

Will consumers find the ads more useful than invasive? That's an age-old question in the relationship between advertisers and consumers.