Since the old motto has become a tired and embarrassing joke, there was a recent discussion the teh Jimmy's talkpage about adopting a new one that better reflects the true nature of WP. The discussion was closed before it even really got off the ground. Which is a pity because Wikiland really does need a new motto.
My suggestion, which I found on a colleague's userpage, would be:
Written by the unwell, read by the unwise.
Any other suggestions?