[dmbaggett]

No corporate development person is going to take a deal to the CEO without having gone through dilligence. So as the selling party, you're forced to subject yourself to this kind of process.

However, you don't have to actually answer everything you're asked in this financial (and technical) cavity search. In one M&A process I participated in, the buyer asked the seller to "tell us your strategic vulnerabilities: if someone wanted to totally shut you down via technical, legal, or data means, how could they do it?" The sellers politely refused to answer this.

Bottom line: there are no rules, and it often seems no one feels any shame doing the most utterly awful, unbelievable things during these M&A processes. NDA's don't mean jack, and if you don't answer enough of the questions, they simply cannot buy you. Choosing which questions to answer, and walking away from all the others, is key.

And, as another commenter said: don't ever need to sell. If you really need to sell, you're probably already doomed.