I also would say no, especially if you only need one pass. They are only sold in packets of 5, and if you can't use them all by 2/29/12 - then they're not even worth the paper they're printed on!
If you only need one, personally, I would forget EBay (or the like). You don't really know what your getting. Even if they show a photo of a pass that expires 2/29/12, what's to say they won't mail one of their "extras" that expired on 2/28/11?
And not trying to be "the legal eagle" here, you are not supposed to buy or sell passes.
What I personally would do is post a request here on AU! It would save you the $15, since many of us have extras, and will offer them to other members for free!