[lleger]

Foursquare – definitely not, but then again I don't use it. Maybe someone who actually plays the game would.

Twitter — possibly. It depends if twitter had the same pervasiveness as it does today. In reality, that's probably impossible: twitter's ubiquity is due in large part to the lower barrier of entrance. So it seems that paying for it reduces the utility of the product and, therefore, makes it not worth the money.

In summary: no.