what's this thing?

To owe your Tweeps a beer, @-reply to tweetbeer like this: 
@tweetbeer @mattallen for the memories
Tweetbeer will let your Tweep know about their cold one and record the debt here for later collection and posterity.
gnoll110 owed a beer to mattallen for the lift to the RoRO Sydney meetup!. about 4 months ago