Like Scribble said, they probably do not read every post of every thread.
And even if they do, part of the whole nondisclosure thing is not negating every rumor. Imagine if they did negate every incorrect rumor. If they suddenly got silent for one rumor and didn't negate it then everybody would know that this was the "correct" rumor, or that it was close. If WotC doesn't give us any information then we can't play a game of "hot or cold" with them.
You may not like it, but companies have very good reasons for keeping us in the dark about upcoming products. Think of the mystery web tool like a birthday present you haven't unwrapped yet and let yourself be surprised when it gets here. And if you find out it's a lump of coal, THEN you can start complaining.
And as I said, they don't have to read every post of every thread, but thanks for implying I meant that
I said that mudbunny and the VCL or whatever they're called
were active in those threads and many posters
did say those things. Now, maybe they think "hey, who cares if we lose subscribers over this, the tool will be awesome and we'll get them back" which is fine. Now, your analogy to a birthday present should be fleshed out a bit more, say that uncle always gets you a lump of coal for Christmas, and one year he's like "let me make it up to you, I'll buy you an XBOX 360, a PS3, an Alienware PC, and a bunch of other really awesome stuff" and then Christmas rolls around and instead he gives you one thing and says "Oh man it's way too much work for all those things, be happy with this". The thing you get is really useful, but you always remember that your uncle promised so many cool things and failed to deliver, plus he always gave you crap before. "This time" he promises "the new cool thing I got will be really awesome" and the present is there, but you don't know when you can open it and based on your past experiences... well let's say your hopes aren't too high.
I'm a huge fan of 4e, the CB, even the monster builder despite its flaws, but damn it would be nice if they finished something (like the aforementioned MB) before rushing off to something new and shiny...
Edit: Just wanted to add that while WOTC doesn't keep their customers informed of what they are working on with any details there are many companies that do. Car companies, video game developers, movie companies, yeah... it build excitement for your product. Heck, wotc really doesn't have any competition in their market space that would "steal" their project and develop it on their own.