The reality is in that most cases, you just change a tagline here and there, recruiters call you, and you just go on and do the next great thing.
The only ones for whom this is a problem are probably the ones with a "nice to have" position and they will have a hard time finding a new job. This sucks, but this is, like you said, also the founder's fault so it's up to the founder to give them a nice severance pay, great recommendations and preferably even introductions to other companies.