Ah, I just read up about that. Yes, it is O.K. to clean your motherboard with water as long as you aren't doing it wrong. By the way, I think he's doing it a bit wrong because I don't think tap water is distilled water... but I'll give him some credit for pulling the battery out.
I don't totally see the point of cleaning out the mobo with a liquid as long as I spray it with compressed air once a month but if there is a lot of fine and resillient dirt and dust then sure, I'll try it with alcohol.