Well this is a no brainer!!

The Buyer should.

Why!!

Because you bought something from him or her..

How can the Seller know if he or she has received the item as described, or is Satisfied with it.

When you buy something at a retail store, who says thank you first, The Seller.

Why!!

Because he sold you something and he Knows that your Satisfied with it, And he handed it to you right there and there, and away you go..

On Ebay, the Seller is selling you what you purchased from him or her by the internet and he's sending it By Via USPS etc, and has no clue or control over the Post Office on when you are going to receive it after it's shipped out, nor does he know that your satisfied with what you bought from him or her when you received it.

So the best thing to do as a Buyer is to Communicate with the Seller, by leaving him or her a feedback of your choice. After all he or she did what they can by describing it, listing it and packing it safely and going to the post office to ship it out.

 I'm sure that 99% of the Seller's will leave you a feedback if you leave it to them.

It's that Simple!! :-)