There was a post by notch ages ago about floating blocks, and how he didn't like them. He said something about not getting rid of them, but maybe making you need to use some Obsidian to keep them floating. Or something like that.
... dammit, where's a glass case full of Enterprise models when you need it...?
Seriously though, that would suck epically. I think I would just have to stop playing if notch took floating blocks away.