Does anybody know the criteria MLB uses when giving out compensation picks?

I'm wondering how the A's got a 1st round sandwich pick for losing Damien Miller, but got nothing for losing Jermaine Dye.

I'm aware of Dye's injuries lowering his numbers but I would think that his numbers even with the injuries were still close to Millers. Maybe because Catcher is a position with lower numbers on average?

Also the Phillies forfeited their first round pick for signing John Lieber, but Lieber missed 2 years before having 1 good year with the Yanks.

Whats the deal?