[onychomys]

That would probably just end up being a map of economic conditions in any given section of town. The seedy parts will be lower rated overall (even if there's a highly rated ethnic food joint or whatever), while the swanky parts will have nicer things. That's my guess, although I think you should still do it, because I might be totally wrong. And interesting patterns might still appear even if I'm right.

[RandallBrown]

Even if it is just a map of economic conditions, that's a useful thing to have.

I could imagine it being a great way to find "diamonds in the rough" too where certain places are much higher rated than the places around them.

[komali2]

If it's based only on Google reviews I think it'll be static. For example, the taco Bell in my hometown has 4.5 stars on Google because it's one of the only restaurants in the area.