"Paypal agents have a lot of work and need to move quickly to get disputes closed so they're not going to start checking video or signed affidavits (anyone could fake sign something)."
The above statement is not true for all cases (and seems to show ignorance of the appeals process). If it is admissible in small claims court (or in a higher court), it is relevent. When you put forth evidence, it is not just the evidence that is being looked at, but the credibility and record of the party who asserts that evidence. Any person who says that it is a waste of time to have a signed legal affidavit and that it is useless to document (with video) evidence of the condition and serial numbers of an item is ignorant of the way the law works. Such documents can be scanned and uploaded so that links can be added to the comments section of the dispute and read by the supervisor. It isn't easy to do this, but it can be done.
I personally know of a situation in which claim by a buyer in an amount of over $250 was reversed to the seller because it was provent through images and video that the buyer returned a different item than what the seller had sent the buyer. Not only that, but the buyer had tried the same scam with several other sellers and therefor had a track record of it. So, when the seller fought back and had the claim reversed this exposed the buyer as a potential mail fraud perpetrator for the first time.
You can easily shoot video and upload it to youtube. In the event I spoke of, the seller actually shot video of the item arriving with the UPS person and with the UPS worker present opened the package and had the UPS worked hold it up to the camera while reading serial numbers off of the item, which were clearly different than the original item sent.
You are NOT completely powerless.
"There is one useful tool to see all the negative feedback a buyer has left."
Not all PayPal transactions are through eBay.
Before sending the item, if you find suspicious feedback left by buyer for other sellers (in which sellers state some injustice was done in their response comment), you should immediately refund the buyer, offer an excuse and an apology, and block that person from ever bidding on items again. Even if they report you, it is better than dealing with the prospect of being defrauded.
However, in a problematic transaction the feedbacks left by the buyer can help to expose the buyer if he or she has a pattern of frivolous claims. If negative feedbacks by the buyer are left and responsed by sellers indicate a seller situation to your own, you need to document this (screen shots) and links to the feedback so that PayPal representatives can easily view the comments.
The problem is that most buyers who commit these scams do not leave negative feedback for this reason. No matter how well you research a buyer you should always document the merchandise in transactions of high value.
