buying videos (or anything on ebay)
My best advice when dealing with ebay is not to buy from anyone who hasn't been selling for a while. Now I know that hurts those who are just starting on ebay but it is a good principle.
If you buy from someone new make sure to ask questions of them to make sure the product is what you want, e.g. for a tickling video that it isn't a copy.
Read the reviews on people and then read the reviews of those reviewing if the information is negative. Large sellers will have some negative feedback.
If you are buying from someone completely new pay by paypal or some other credit card service. If the product is wrong or defective and you can't get a refund or replacement, dispute the charge. If you have an American Express card USE IT. AMEX offers the best protection for consumers online.
Sometimes you may want to write to those who have bought from the seller to get more detailed feedback.
If something is too good to be true, it probably is.
Before writing bad feedback try and resolve things with the seller. Problems do happen (computer crashed, family member died, etc.). When I made a mistake and did not send something ontime I made ammends by sending an 'extra.'
Also read what it says on ebay in the help area for buyers.