The hard part here is "ultimately shown to be dishonest" - who is privy to what is said in boardrooms and sale negotiations? How about just examples where the investors managed to get out just before the bubble popped?

The canonical example would be Broadcast.com, which made Mark Cuban a billionaire.

https://en.wikipedia.org/wiki/Broadcast.com

1998 IPO at $1B valuation

1999 bought by Yahoo! for $5.7B

2002 shut down