I never did get the logic behind Thor the Unworthy. Some secret that Nick Fury whispered to him caused him to stop being worthy of Mjolnir. Even Odin is unable to lift the hammer now (which is silly considering that it was Odin who made the enchantment.)
I don't know if I'm mixing stuff up but allegedly, the big secret is that Odin has a daughter? I fail to see how that made Thor unworthy. The condition is whoever be worthy, not whoever be the firstborn. (also, there's the thing about not knowing he's unworthy allowed him to lift the hammer?)
