I've set up this blog for you to announce *updates* to your web 2.0 app. Send me your updates by email or post them directly to the blog.
web2loop.blogspot.com
web2loop.blogspot.com
How about you manually contact every Web 2.0 startup asking them for data to populate your blog with? That will make more sense: if you in need, you go out and ask.
If enough people contribute to this blog, it might become popular thus providing these people with a source of traffic.
So in essence, people would contribute to this blog for the same reason that they would contribute to freshmeat.
I, for one, plan to use it as soon as we launch our startup. Unfortunately it's not much good if you're not ready for traffic, but I think it'll be a nifty added source of exposure.