[apu]

Norvig's talk at Startup School '08 went into more details on this: http://www.youtube.com/watch?v=LNjJTgXujno

They do use SIFT (or at least a variant thereof) for finding and describing interest points, but by itself, there is no geometric matching in SIFT. There are various competing approaches on how do it, although in many cases, you can get very good results even without it. (It's very slow to do geometric matching so people often skip that step, or only apply it to the best matches.)

Landmark detection is a recent "hot topic" in computer vision, and given a large enough dataset, it essentially works now for the most part.

[bfrs]

Thanks for the link.