I did not know that feedback was an option/not required as I have seen many sellers state they will not sell/accept a bid from someone with a score of 10 or less and one required a score of 20 or more. So, that being the case, feedback is required and a buyer has little option but to be positive in order to get a positive/or any feedback at all from the seller. 

I almost always pay that same day and I personally would like that to be the feedback point as the buyer. I cannot give feedback to the seller until I personally see the item. I don't go by anything anyway, other than that number after seller/buyer's name. Obvously many others go by that. So in that respect, feedback is NOT optional. I believe that it is in essence sort of a blackmail affair and I don't really like it. The numbers could just go by the number of sales each has had.

Just my opinion, thanks