The reputation engine built into Ebay seems to be taken very seriously. OTOH as someone who has avoided joining Prime, typically waiting until I have enough purchases to qualify for free shipping, I've experienced constant nudge (the increase in free shipping sale amount moving from 35-50, the obvious skew towards Prime in search results) shopping at Amazon in the last two years. I'm just suggesting that for me, having a philosophical reason to support Ebay over Amazon (democratic, bottom up, vs. top down) will help assuage the nuisance factor.