Its not a whole lot of effort to write it on with a permanent marker or put a sticker on using a label making machine if you're worrying about permanently damaging your board. I've heard of an incident where cops went searching for a missing kiter because a board was found (they wouldn't know its a common occurrence) and at least if there is a name and number on the board, its easy for someone to verify you're not missing.
There is also the added benefit of the finder being able to contact you.
Now you tell me.Never thought of it cos I use bindings and my board hardly ever comes off, just got over to Rotto and found my board had fallen of the boat on the way. Sure wish I had my number on it now 
