I wish I could be as optimistic as most of the other posters, though I hope that they are right and I am wrong. But, I think the guy has something. I don't know what it is, but he's got something. Someone is paying an $800 an hour lawyer to spend a lot of time covering Walsh's butt. People don't do that unless there is something to be gained. If the lawyer's doing it for a cut rate, then he's confident that he's going to be at the center of a big story at the end of the day.
The problem is that we can discredit Walsh all we want, claiming he defrauded the Pats (to most fans outside of NE, that's, unfortunately, like saying someone defrauded the IRS--"good on ya, mate") pointing to his checkered employment history and the low-rent, malicious prank he played on his friend and his girlfriend in college. However, the rest of America isn't going to pay more than fleeting attention to those things if he has something on Belichick and the Patriots.
IMO, the best we can hope for is that he has a few tapes from the period during which Belichick has already acknowledged that taping occured. That would create another media firestorm, ESPN and the local newspaper whose name we don't mention would play them endlessly on TV and their websites, but ultimately they won't do any more damage than create further embarassment for the team.
However, if has a tape of the walkthrough, even if it was 'unauthorized,' we are toast. No one, outside of people on this board and other true fans, will believe that it wasn't sanctioned by Belichick or Adams.
As I said, I hope I'm wrong.