IndyMedia is reporting that Bikes Against Bush creator Joshua Kinberg - this is the guy with the bike that spray-chalks anti-Bush slogans behind his moving bike - was arrested while giving a demonstration of the vehicle for MSNBC's Ron Reagan. While a sergeant on the scene agreed that the wash-away spray chalk probably wasn't defacement of property, Kinberg was still arrested for an unknown charge. As of last night, he was still in custody without yet having been charged.
The Indymedia story also has a link to a torrent showing the arrest.
Read - Activist bike creator Joshua Kinberg arrested [NYC.Indymedia]
Update: Apparently he was charged with vandalism.