I'm sure Google promised these founders all sorts of things once their application was assimilated into the borg that is Google. And with lots of money on the table I'm sure the founders grinned and asked where to sign.

Closing your doors to new signups is practically like suicide. As a founder I would never agree to that if I was taking a smaller buyout in exchange for continuing to work on my application as an employee of Goog.

Now if they backed up the money dump truck and sent me on my way I wouldn't care so much (although I'd probably have thousands of users who'd hate me but probably also wouldn't blame me)