[gcr]

Or, set the price to be a function of the number of messages the sender sent per day.

E.g. If I've sent `s` messages per day averaged over the last N days, the next message that I send should cost (rounded to the nearest penny):

   1.01^(s-1)

That'll put a damper on it right quick. Sending 100 messages will cost $168.79, sending 200 will cost $625.35.

[loceng]

I don't see this happening, as Facebook has no trouble abusing the userbase.