There are a lot of scammers these days. It is not a problem specific to eBay. There are many stories in the news of people who received messages from institutions that impersonated their banks and have lost all their life savings.
We always have to be extremely cautious these days. If you landed on a site impersonating eBay, you either clicked on a link in a phishing email or it was the infamous fake eBay Motors on Facebook.
It is not eBay's responsibility though, or the responsibility of any other institution. If somebody impersonates you for example, you would not consider yourself responsible either.
Ebay does warn people in their help section. They explain (for example) that their real messages are also on eBay (in your inbox), so if an email you receive claims to be from eBay but is not in you eBay inbox, it is most probably a scam. This is just an example. There are more warnings.
