No worse than tokens sitting on an exchange somewhere. A simple cap on the number of DAO tokens the tipbot can hold for each user would solve this. If the cap is exceeded, the user should be prompted to withdraw enough tokens to bring them below the cap.
I'll put up the 1000 DAO I just received as a bounty for a functioning DAOhub tipbot. It must at least support ETH and DAO tipping, and should not charge any fees/take any commission.