"Bitcoin" is a danger word to eBay/paypal. They've even circulated internal emails (that have been leaked) saying that the (currency) is high-risk in their eyes, which carries many implications especially if there is a problem with the transactions between the seller and buyer. It does not matter to them if the transaction is made using bitcoins, the trade is for buying/selling bitcoins themselves, or if its bitcoin related hardware: it's all the same in their eyes.

Sellers might be able to get away with it if they don't specifically use the word 'bitcoin' or 'BTC' in their listings.