Development of Creative Commons licenses

["Greg London" <email AT greglondon.com>]

I can't seem to find anything on the CC website to
explain why the Public Domain dedication (PDD) requires
you to give CC your email address etc to get the license.

Is PDD not like a license that you put on your work?
Do you assign copyright over to CC or something?
Or does CC put the extra stuff in the way just to make sure
someone doesn't use PDD without knowing what the heck
it is they are about to do?

I'm nearly finished with a work and will either be putting
it under CC-BY or just go with PDD and noticed how different
the interface to them seems to be.