At one point, (and I think now as well) placing auctuons or buy-it-nows for pre-orders were against eBay policy. You had to have the item in hand at the time you submitted the auction in order to sell it. Even with good feedback, I still wouldn't buy a pre-order on eBay just in case. I've seen a lot of sellers that had pre-order auctions get kicked from eBay for other reasons, then you have little to no recourse in getting your money back.
Also, Paypal will only fight to get money back within 45 days of the auctions end, and eBay itself will help for 60 days after the end. A lot of pre-orders fall outside that time range, so you're pretty much out of luck if it's over 60 days.