If I "Shift" an enchantment which has a Magebind +X from a non-Mage to a Mage, is there anything that should cause the Magebind cost to go into effect? I doubt anyone is going to use Shift Enchantment just to avoid the cost (Regrowth, Shift Enchantment is the same cost as the Magebind. Harmonize is only one cheaper, and extra spell out of your book, plus the extra casting...), but it's certainly possible, especially as the game grows and cards come out that make the exchange a little more valuable.
I'm honestly more curious than anything... Like I said, it's not going to break the game at this point, and I'm certainly not looking to have it do so.