[sbilstein]

Well, in this scenario, you are actually the 'former' colleague getting recruited to be a co-founder while the other folks stay stable. You just admitted you would and I wouldn't be surprised if there is a PM or even another engineer who would want to join forces. That's different than a complete stranger recruiting you -- I would be very wary.

[kevstev]

This was a real scenario I faced and the company/founder was a complete stranger to me- I forget if he just found me on LinkedIn or it was through angel list- I would not have been a cofounder just their CTO. Either way I ended up taking another offer with somewhat lower risk- they were extremely successful but turnover there was on the order of 25% per year. And I did end up taking some people with me and lasted about 5 years there so it all worked out.

I check in to see if the other company ever made it anywhere and nothing ever comes up so I guess I wasn't missing out on startup riches.