If the maps were popular in SC1, Blizzard didn't offer any compensation for the map makers back then either. Back in SC1, Blizzard still owned all the maps that were made with their map editors, for their game. Map makers weren't allowed to legally sell their maps. That hasn't changed. And another DotA can still happen. Though from the e-sports community, it seems like they're trying to get Blizzard to amend that, but not a lot has been stated publicly about it.
No compensation, but they never ended up simply saying "We're going to take over this map because it's popular" in Starcraft 1 or Warcraft 3. More or less, they allowed mapmaking to continue on its own path, evolving without restriction and resulting in a lot of innovation; if you look at the original Blizzard custom maps, as opposed to some of the masterpieces that came out during the heyday of Warcraft 3, there is no comparison. The original Starcraft is such a long ways back, I'm not even sure why you bother referencing it; the similarities between SC2 and Warcraft 3 are much more apparent, which makes the differences between the two that much more drastic. It's the equivalent of being given the Internet at its fullest, then moving to China where everything is nice and censored and geared toward making everyone happy, since they can't do anything about it.
And yes, memory size of the map (10 maps, spanning 50 MB total) is the entirety of what you can upload. DotA, the original, which made extensive use of ingame textures, sounds and effects (and had 90-95% of its map size being custom coding on skills) neared 10 MB on its own before IceFrog had to start doing some cleanup and compression magic. Anything beyond the complexity of a MOBA or tug of war game won't be as viable, which is a pity in the updated engine.
As far as the UI, I think he means the rather horrid change of making "popular" maps show up first; anything past page 2 will rarely be able to get a game going. Most of those on page 1 and 2 are simple games where you control a single unit, as popularized in DotA, and most people don't even bother joining anything that's reasonably in depth. Civilization? Diplomacy? Staples of the non-DotA custom map genre? Again, if its too complex, it doesn't get pushed to the top because people want instant gratification and simple mechanics. Nothing new survives anymore, and I'm more likely going to get a decent game going on Warcraft 3.
And for the censorship... if parents want their kids to not be exposed to these sorts of things, limit them from playing the game in the first place. It shouldn't have to fall on a company like Blizzard to hold hands and sing kumbaya so the kiddies won't get treated to hearing they play like crap; it starts from the people providing the games to their children in the first place. The swearing censor is one thing, and that can be turned on or off at will, but restricting mapmakers just because someone might see the word "God" in there is pretty ridiculous. That's not even counting the ability to use (and abuse) voice chat, sound clips, and other means. It's like attempting to stop sites of questionable legality on the internet: For each one down, three more pop up in its place, and it's a fruitless attempt to control it. Mind you, this is in a game where character pictures smoke, say "ass" and various other things that would be against their terms of service if someone made a map containing them, but
it's okay to break the rules if you make them.
Blizzard has simply fallen, from once a good company that got its roots in the trust of consumers by providing an excellent service, to simply being an antithesis of consumer confidence. Yes, I'm still slightly bitter about the whole ordeal. But as long as people keep eating the shit Blizzard dishes out, they'll keep dishing out shit. Because money.
Guess there are indie games, and Warcraft 3 servers are still around. If only the guy who made Genesis of Empires 2 would fix it for the Warcraft 3 patch that broke it...