According to The Miami New Times, MLB is launching an investigation of Miami Marlins starting pitcher Jarred Cosart concerning gambling.
The investigation was launched because of activity on Cosart's Twitter account in which he allegedly sought advice on gambling. After this created a Twitterstorm, Cosart subsequently deleted his account although it appears he has launched a new Twitter account in which he claims his old account was hacked and that he would not bet on baseball. However, the new Twitter account has not been directly confirmed by Cosart as of this writing.
Although I suppose MLB has to look into this, it looks like weak tea to me. The messages involved anonymous Twitter accounts. They do not demonstrate that Cosart actually made any bets. If it does turn out that Cosart gambles then there's a good chance he is betting on sports other than baseball. I think it's far more likely that people are betting on college hoops than spring training games.