Thanks so much for the feedback! I really appreciate it. I do plan on adding keyword alerts at some point, so that you can just follow super targeted stuff, as well as search. I may add some more granularity in the categories, but I don't want it to get too overwhelming to post or subscribe.
In terms of a niche, I haven't spent much time thinking about it, but when it comes down to it, this is essentially a general anonymous message board like Craigslist, so I'm sure there are tons of niche applications. I'd love to hear more ideas from folks.
I don't know about your "social" position on the web, or better in the real world. But if you can link some known great engineers, angels, VCs, entrepreneurs, and independent journalists with non-backed (not funded only) startups, that will be great. Perhaps linking a startup with a strict small group of top people.