As Amie mentioned, it seems like 50% feedback is average. Personally, I don't think buyers think about leaving feedback as much if they aren't also sellers. When I buy on Etsy, I love leaving feedback. When I buy from Amazon, I never do! When I've asked buyers for feedback, some have convoed or emailed me. I think a lot of buyers aren't even aware of it, which seems odd since it pops up right when you log in!