@joe1225us
When it comes to
ebay the buyer must beware.
ebay is a massive global market that isn't necessarily centered around the utmost standards and so when it comes to purchasing stamps its hard to fault the general market on a few imprudent sellers.
Regarding CK or NY - I've always shied away from their auctions as its apparent that their lot descriptions lack the type of detail that you would expect from a dealer handling such a large amount of volume.
While they are certainly not the only ones at fault - though I would hesitate to say that 80% of the stamps have undisclosed faults (as that has not been my experience) - again, you really must be careful to scrutinize the lots that you are bidding on especially if they are going for a good amount of money.