How can a scammer take over a site that has done a lot of trade "over one year ago", so lots of items sold, but nothing for 12 months, and then start listing high value items with photos & descriotion text lifted from recent genuine sales.
Accounts can be hijacked by scammers in many different ways. Phishing is common, despite warnings not to follow blind links in emails. Some users reuse passwords and email addresses as usernames on multiple sites, and if one site is breached the other accounts are in danger of being hijacked. Some users choose common passwords that are easily guessed, or have security questions based on publicly searchable information. If someone can gain access to your email account, it is often trivial to reset passwords on many other associated accounts and then delete any evidence.
eBay can do many things and provide numerous warnings, but eBay cannot stop a user from responding to a fake email and providing credentials directly to a scammer. If the user happens to have been a seller that is not currently selling on eBay, the user's account is a prime target for scam listings, which are often just copies of legitimate listings posted by others.
Users should take steps to secure all their accounts -- particularly any that are linked to financial services -- use secure passwords and not share passwords between accounts, and avoid falling for phishing scams.
Buyers on eBay can entirely sidestep many issues by choosing only to do business with experienced sellers that have received recent and past positive feedback for selling similar items in the same category, and by avoiding new or unproven seller accounts, or accounts that have unexplained gaps in selling history or drastic changes in seller behavior that might indicate a hijacked account, deals that require users to violate eBay policy by contacting the seller outside of eBay, or any deals that appear "too good to be true".
