Why you cannot add amazon and ebay in coinrebates? Anyway, Amazon and Ebay are most likely bitcoin accepted as mod of payment to their site. It's been once that I tried to buy a ledger in amazon site shopping online.
It is something very usual and the people who are use to with the bitcoin and them are aware of the bitcoin. The price of the bitcoin will be high when more people will buy and they will use the Amazon and he eBay. I did not yet buy anything online but my friends use the bitcoin online shopping they know how to use and how to invest.