I don't mind this. I like controlled systems because they tend to keep the garbage out of my sight (steam, itunes). If they allow the masses to create really obscene things, it only hurts the developers that spend countless hours creating quality mods and maps because the consumer has to wade through trash 98% of the time.

Another point is that the game is still new. That 25 MB limit is probably not a hard limit. It 'could' go up if they start seeing a show of hands with people needing more space.