The service, which recently passed five million users, is coping with the challenge of maintaining a great atmosphere among a disparate community of users. 

Most of the rules are straightforward enough: no spamming, no cuss words, but one rule stood out: Foursquare asks users not to check into strangers' homes.

"Home venues are sensitive and it can creep people out to see non-friends checking in. Remember, checking into your own home is ok!"

Hmmm, aside from the rare super geek pad in Brooklyn, why would users be checking into strangers' homes?

Maybe Foursquare should read up on nudge theory and try to de-incentivize this kind of behavior with a new "Stalker" badge. 

bpopper at observer dot com - @benpopper