User blog comment:AYET/The Mera Mera no Mi and Doflamingo/@comment-4530178-20130307103030

If I'm right, didn't Doflamingo mention that Luffy would want to get the devil fruit of his brother's or somethign. Correct me if I'm wrong, but if that's the case his motive for keeping it may be to ruin Law's plan by getting Luffy to come after it.