> brand name

The founders have themselves said that they have little traction, and 3rd party payment services will not add much value.

> domain name

Doesn't matter, when brand name isn't useful

> Existing code base

Its takes significantly less time to build it the next time.

> Registered users

Facebook has 250 million users! <1% cant matter anyway.

Right, and that's why no one was interested in buying the company.

Investors own the company, not the employees--even if they are founders.

I don't think Facebook needs the domain, code or registered users. They liked the idea and obviously the people behind it. But to launch it on a Facebook like scale it would need a rewrite, tons of legal power and probably a new name anyway (even TipJoy learned to not like their name).