Are there any rules regarding check ins?

BFLN (Beers from Last Night)

Sure - we all forget to check-in to Foursquare sometimes. When your drinking - chances are that you'll forget 100% more. We are not going to be coming after you if you check-in the morning after a long night of drinking - we let the user decide if they want to add it. Keep in mind that each check-in is tagged at certain time by checking in early or late - you might be loosing out on badges or rewards.