BigMusky - I've only played in mixed leagues, but it does sound like a good idea to take advantage of a worried owner. With a guy like Baez, who's almost guaranteed to be traded, it might not be such a good idea. But as for Burnett...it's certainly possible that he'll be traded, but with Beckett's health uncertain at best, I don't really think the Marlins can afford to lose Burnett if they hope to make the playoffs this year.
Still, there are enough teams interested that there's always the risk of a trade. So basically, I obviously wouldn't give his full value, but if you can steal Burnett for garbage like Derek Lowe or something like that, then jump on it.
(That was partly a joke, but honestly, if you think about how few trade rumors actually end up coming true, I'd personally rather chance it with Burnett than have a high-WHIP, low-K pitcher like Lowe.)