I think that's a reasonable estimate. It could be a lot more though if they can get the kinks worked out of the site and HF20 delivers on simplifying the onboarding process.

Personally, I'm not evangelizing until those issues are in the rearview. Once they are though, the gate is open because once it's easy for people to invite their friends and joining up is as simple as it is on any other site, this thing will take off real quick.