I think it has to do with how "standards" are really created: a browser manufacturer creates a new feature, it gets popular, other browsers copy it and then the standards group proposes it as a standard.
But until it becomes a standard -- after everyone agrees on its syntax -- the only safe way to use a new feature is to use a proprietary prefix. Case in point: the current Webkit gradient syntax is completely different from that of Mozilla and Opera. There would be no way of handling this without -webkit-, -moz- and -o-. (And the IE filter version, of course!) -- <http://forum.pspad.com/read.php?2,56464,56467> PSPad freeware editor http://www.pspad.com
