Ex-TWer and current TW shareholder here. US securities law does not allow a company to be private over a certain number of shareholders. The owner couldn't legally offer to sell the company to all 4000-some employees, even if they all lived in the US. (They don't live in the US, which makes it much more complicated).

Goldman Sachs tried to end-run around this limitation with Facebook, but failed: https://www.theguardian.com/business/2011/jan/17/goldman-sac...

There are other restrictions: you cannot sell shares of a privately held company unless the prospective buyer makes over 250k per year or has a net worth of $1 million.

All of the above are SEC rules. There are numerous other hurdles.

That's an interesting question, in a services business like this there is very little value without the employees.