I think the Sharks get to do due diligence after the deal is made. They let pretty much anything interesting on the show for obvious reasons and quietly terminate deals later down the line as needed.
I'm sure it's hard to find companies for the show, and it would be harder to find them if you did due diligence first.
Really? If I had a company, I would fight to get on that show. The exposure is reported to be worthwhile if nothing else.
Correct. And in many episode's they also said how some shark "backed out after agreeing verbally to a deal during the taping of the show.