Andrew Boon
"There is a huge untapped market for "niche" social networks."

Indeed. One could penetrate hundreds of niches using SN-site, based on locality, interests, segments, etc. It hasn't even started now. I can't stress enough how much more rewarding it could be to target a small niche first instead of aiming at MarkZ's head.
Below is the legacy version of the Boonex site, maintained for Dolphin.Pro 7.x support.
The new Dolphin solution is powered by UNA Community Management System.