The Rays used spring training to learn when runners can take an extra base on a hit:

But manager Joe Maddon has taken the reins off even more this spring, putting an emphasis on getting better at two key base-running plays: advancing from first to third and scoring from second. He doesn’t care if players are thrown out trying to take the extra base in camp, as long as, by testing their limits now, they learn how to be smarter come opening day.

I like this. Maddon wants the team to be aggressive on the base paths, but not to the point of hurting the team. This should keep opposing defenses on their toes.