disclosure: i'm currently selling a printed map (kickstarter.com/projects/1147214836/toc-guide-to-sf)

I think social data is much more useful as a filter for a curated list than it is when used on the set of ALL establishments in a city.

If the list is prefiltered to only include establishments that are at least excellent examples of whatever they are trying to be, social data is a useful way to figure out what to show the user.

Seeing what places my friends have been going to is much much less useful to me than a carefully assembled list of excellent places. For a great example of this, see "Tokyo by Tokyo." _much_ better than any social algorithmic solution can currently do.