I also have no problem with the way pg is doing things. However, the flack he's getting is starting to reach epic proportions. Perhaps the following quote from Kent Pitman at Lisp50 explains it: "Soliciting volunteers gives critics something to do, which dilutes their passion, pacifies them, and makes them feel involved." Conversely, if they feel they have nothing to do, or their work isn't appreciated, they become critics.
I'm not sure the use of an open forum has been much of a success so far. When pg first announced the existence of Arc, he asked people to email him with suggestions. People were supposed to suggest features from other languages and then give examples of how that would make code shorter. Eventually, he posted all the replies on his web site, and although there were lots of ideas, not a single person had actually done what was asked. This forum has been better, but far from perfect. For example, has anyone has actually tried to write a fast profiler yet?
I think that if you want to offer a language to the community, and expect useful work out of it, you need to provide a structure that people can work in. For example, Perl 6 started with an 'RFC phase' and then moved on to 'Apocalypses'. Writing an RFC forces you to put a lot more thought into your ideas than you would if you were just posting to a forum. Writing the Apocalypses made sure that there was plenty of feedback on these ideas. People had something to do and knew where they stood.
So I don't think it really matters whether you release a compiler. What matters is whether people have a structure they can work in. That's why everyone wants to write libraries for Arc. Writing a library is something that one person can accomplish. It's a structure that channels people's energies towards a given end-point, and they are rewarded through people using the library in their own projects.
For Arc, the compiler was both a help and a burden. It helped because people could actually try out ideas. It was a burden because everyone started working on the compiler, not the language.
So I think community-aided design can work, but it needs to be harnessed correctly. The most important ingredient is probably high-quality feedback on what people are doing. Of course, that also requires the most effort, but no one ever said it was easy. :)