I put together a similar bot that either responds to a recent #fml, or sends a pseudo-random account an unsolicited (hopefully) cheer-inducing missive (from a bank of 200). Runs at a random minute once an hour. Not been banned as yet:

https://twitter.com/KudosBot‎

Previous interactions visible on Topsy:

http://topsy.com/s?q=Kudosbot