When this happens, think of the convenience! All you'll need to do is look at the nearest camera and give a thumbs up, and Facebook will automatically mark that you Liked [whatever you're standing near].
Two people could become friends by finding the nearest Big Brother station and doing a thumbs up together.
One of (many) problems will be how they contextualize all that data. You know, this started as a joke, but seriously, if Facebook had a feed of this kind of data, it would be interesting to see the hypothetical profile they build based on what they would see an individual near vs. what they claim to like on their public page.