eBay was the biggest innovation of the Dot.com era. It took the yard sale online and gave it world-wide potential. It permitted mom-and-pop or smaller concerns to have a catalog accessible by millions. And by taking a small cut of the action eBay has an enormous revenue stream that permits continued upgrade and acquisitions. eBay will not insult its customers as Facebook has - that would threaten this revenue stream.
In the early days, eBay was a great place to sell. I even sold a crappy 50/50 Renn & Stempy T-shirt for $41 once. Nowadays the prices have plunged so now I mostly buy rather than sell. A lot of stuff is cheaper even with shipping (often with free shipping) than buying in stores. Facebook I just don’t get what the economic value is.