It is both a "4" (upright) and "f" from right almost similar to its favicon. Very creative confluence.

Sadly it can also be seen as facebook nailing down the 4 in a square.

So when will Facebook invent something new?

The place marker icon is from Google Maps. Yeah.

Every time ppl sent me 4square invites I would ignore after seeing the logo.

I kept thinking it was some sort of Dodge ball game

Four square is a dodgeball type game.

http://en.wikipedia.org/wiki/Four_square

The name for the service was a consequence of it being the follow up to a social networking service called "Dodgeball" that was bought out and killed off.

just like those guys that see jesus christ's face on a toast. yeah.

A square rendered in perspective would get a trapezoid shape like that.