I think that is the worst idea ever. It is not a currency, it is a commodity. The value fluctuates too wildly, and it's not backed by anything. Also, two major exchanges are not allowing withdrawals at the moment.

It doesn't really hurt Mockingbird in the end, though, and that's the worst part. It hurts the donor. If bitcoin tanks, which it will, or if you can't access the funds, then it's just a donation that you may as well have not gotten. On the other hand, the donor could have put a lot of cash into the bitcoin, watched its value plummet, and realized that he didn't really make a donation at all and is out of the money.