I got Matt Cain in a dynasty and claimed there would be no way I'd ever trade him...he was gone within a week in a blockbuster 6-player deal. I then had Sizemore and said there was absolutely no way Sizemore ever leaves my team (Especially since I am a huge Indians fan), just pulled a deal to get rid of him last week.
The moral is no one is untouchable if you think you're getting the better deal. The deal of Cain net me Soriano while Sizemore brought home Abreu. Any deal could be donme, it just takes the right amount of players.
Sean Tracey has my apologies, we all know Ozzie Guillen is an idiot. I'm rooting for you!