Swamperbob is clearly very knowledgeable and very highly regarded.
With all due respect, I would like to express some more of my concerns. I have low tolerance for cheats and frauds, and have some strong feelings regarding the importance of combating fraud.
ebay is a public marketplace with very large numbers of novice collectors. Buying fakes not only provides support to the fraudsters, but the negative effects of endorsing their products -- in a public marketplace of naive buyers -- are amplified.
Suppose I'm a novice collector of Pillar dollars, and I buy most of my coins on
ebay. Novice collectors often look to what the more experienced bidders are bidding on. Experienced collectors are often "shadowed" on
ebay by newbies. I notice there is a bidder with a high feedback and a long history on
ebay who consistently outbids me or snipes me in the last few seconds on what I consider the best deals, which is actually fake junk. Novice bidders tend to get emotional about their bidding, so I decide I'm going to win, whatever it takes, and bid every fake higher or set my snipes to a ridiculous level.
So the crook not only gets your money, which translates to support for expansion of his criminal behavior, but he gets the fakes bid up to ridiculous levels. As Susanlynn has pointed out, bids beget more bids. I have seen examples of worthless modern fakes of ancient coins (offered by crooks) bid up to much higher levels than good quality authentic coins of the same type available at the same time from honest dealers.
So the dealer of fakes gains credibility, because so many collectors have supported him publicly by bidding in his actions. Bids from a few experienced buyers and many bids from less-experienced buyers in sheer numbers are in effect a validation of the seller and a de-facto authentication of the coins he sells. They say "I buy from him, you should too."
The cycle continues, and things get worse. More newbies are led to the slaughter, they eventually find out they have been duped, they get frustrated and quit the hobby, while honest dealers lose business.
Fakes are also showing up at coin shows and in dealer's stocks everyday. The technology is advancing rapidly, for example the new blast casts are often very difficult to defeat, and sometimes even get past the experts. You can go to coin shows and examine these fakes in hand to gain familiarity with them. I see many fakes in ancient and world coins at coin shows. I don't need to buy them to study them.
Experts who can spot fakes on
ebay should report them to the users groups on
ebay and yahoo who discuss forgery detection and fraud prevention. If a pattern of selling fakes is detected, these sellers' ids can then be added to the blacklists. The sellers should also be reported to
ebay by the experts to get them kicked off or at least the auctions ended.