Creative Commons Scuffle

This thread on Metafilter has once again made me wonder what the actual point of the Creative Commons is. I've looked at the Creative Commons before and had it recommended to me and have seen the licenses around on other sites for a while. But being a dumbass, I don't really understand how it's different than saying "do whatever you want with my dumb junk, I totally swear to god I won't sue you".

Are the Creative Commons licenses in any way actually legally binding? Is there anything preventing people from just changing their minds at any point? I assume the existing copyright laws overrule any pretty license button you may decide to put on your web site.

Maybe the purpose of the Creative Commons is simply to explicitly promote collaboration between artists. In that way I can see it being kind of handy, though I imagine there are other ideas that could be more effective for that.

So I don't understand. I also don't quite understand why people who aren't making any money off of their work worry so much about getting ripped off, but that's a whole other story.