this give advantage to buyer..
however a risk to seller is that they might be a lot of joy buyer who just wanna try and play around with the gadget/stuff..
for e.g.:

seller selling a brand new box sealed gadget.
buyer tried the gadget during COD and thinks that his current gadget still works as a charm and not much different from the new gadget.
buyer refuse to pay and rejected the item.
seller rugi since need to pay for postage+box opened+no deal+ hell lot of trouble..

Lølz..how long the buyer need try the thing and within few minutes can do comparation? I dun think this is fun a buyer playing like this.. And which buyer so free doing such a long time for playing a seller.. the seller can blacklist the buyer address and name or ic so other seller wont trade him anymore..