I think most know they're selling counterfeits...they just always have a canned answer that seems half plausible.
Either way, you have eBay's buyer protection. I'm the kind of person that trusts before they mistrust(aka gullible) so I wasn't really angry when I found it was a fake, just upset.
But true, the number of people knowingly selling fakes will be higher than those who don't know they're selling fakes. Just make sure you're well informed and you'll be set.