Many of the obvious scams can be avoided before a purchase is made by checking seller feedback and knowing what signs to look for. It is not enough that a seller just has recent transactions or a good overall feedback percentage.
Many scammers have 100% feedback right up until the time that shipping deadlines start to get missed, then the negatives start to roll in. Scammers often try to sell many items as fast as possible to maximize profit before users start to notice problems. That is one reason why scammers often advertise items at too-good-to-be-true prices: the need for quick sales before the account is shut down or negatives appear.
Many scam accounts have little or no feedback -- those are easy to avoid.
Some scam accounts have feedback for purchases but none for sales. Of course all sellers have to start somewhere, so if you avoid sellers with little selling feedback you may miss out on a good deal from a new seller. But there are often other good reasons to avoid buying from new sellers: new sellers may need additional hand-holding going through the selling process the first time. New sellers may not understand payment holds or may have shipping issues.
Some scammers have feedback for past sales, but the sales may be for an inexpensive items such as keychains or one type of clothing accessory, sold in single quantities over and over again. The fact that someone has sold keychains successfully does not give you any reason to believe that they will be able to deliver expensive electronics.
Some scam accounts have feedback for sales, but the sales may be private (in which case the items or prices are not displayed in feedback). See here for possible red flags you may notice in such an account:
https://community.ebay.com/t5/Buying/How-to-read-a-seller-s-feedback-page-and-spot-a-fraudulent/td-p...
In some cases, a scammer can hijack a legitimate user's account; then past feedback from prior to the hijack will tell you little about the behavior of the scammer that has taken over the account -- unless you can notice a change in behavior between the old feedback and recent feedback or the current items for sale. You may see a large gap between previous feedback and little or no current feedback, and past items bought or sold may bear little relationship to current items listed.
In one recent case I remember, a professional bicycle seller's account was hijacked shortly after the seller had stopped selling. The hijacker listed multiple quantities of new bicycles at very good prices with free shipping. Because the seller's account had excellent feedback for past sales of bicycles and appeared to be a pro shop, even though there was a gap of many months between sales, many users ordered from the scammer.
That sort of hijacked account can be very difficult to detect, but many other scams are much easier to spot, since many scammers are lazy and go for the quick buck rather than planning for a long term scam.
