I didn't see a conversation on this in the comments, maybe I missed it, but I think one of the reasons why you don't see as much creative control over web pages is spambots. Lots of things that I've put up on my own personal web page that let anyone add things to it also allowed spambots to invade. And since most software to repel spambots needs to be rather advanced to work effectively, you see instances where the user content part just keeps locked up until it's closed completely.

This is a problem that big companies can solve, but it's much trickier for one guy with a web page to solve.