Just out of curiosity, are you a startup, a non profit or a guy doing a side project?

We're Investling, which is a handfull of startups and an IT consultancy. We're for-profit, with some non-profit projects on the side (in part because we'll make more profits if we can help save the world from surprise conversion to paperclips). The majority of our non-profit work is SIAI related.

I predict the site's userbase will not explode overnight but will escalate in the shape of a hockey stick. […]

Some projects follow that pattern. Some projects never hockey-stick. How can you tell which curve you're riding?

We have many projects running: some have maintained exponential growth since we became involved; some are too young to judge; and some are on the low end of a curve that may be a hockey stick and may just be a project that doesn't have any legs. I very much hope that the LW crowd will latch on to PBook (keep coming back, tell your friends, etc.). If you do (we do - several of us are very keen LWers) and we see traffic growing, we'll flood more resources into the project. If it languishes we'll continue to host it and may even open source it, but it seems more sensible to flood our resources into projects that are winning. I really don't want to see PBook die, but I'm trying to count warm fuzzies consciously.

Also, you need to add documentation […]

We know the documentation is sparse (or, more precisely, the user interface isn't intuitive - documentation is evidence of a UI failure and good design is self-documenting). If you guys are still around in 14 days we should talk about more dev resources.