These sellers are getting more clever. Most of you will remember the stories about how a few years ago the market was flooded with J-Nugg forgeries. eBay was the prime place those forgeries were being sold. At the time they were being passed off as the real thing. It obviously didn't take Ebay long to figure this out and start shutting down auctions from sellers with known counterfeit goods. The "Wild West" days of Ebay are over - nearly every item they sell now has their "eBay Buyer Protection" coverage on nearly everything they sell, in order to shed the stigma it used to have about buyers getting defrauded by bogus sellers.
The forgers, in an effort to step around this, started selling the forgeries as "replicas". The problem was (and is) that these replicas were poorly represented as such - usually a single mention at the end of the description and no mention in the auction title, combined with bogus claims of rarity, value and quality. The green J-Nuggs just recently yanked which triggered this topic also are examples of the tactic of offering forgeries in the colors that the originals were never made in - like the black J-Nugg forgeries that have been circulating. The forgers then believe they can try claiming there's no way their product could be confused with the originals because of this - despite the deceptive marketing tactics to the contrary. In the end, eBay takes a dim view of these attempts and usually shuts them down as quickly as they can detect them.
As far as the Buck Twins' friend showing off his "replica" collection, well - just like there are people who collect stamps, paper currency and coins, there are also a subgroup of them who seek out misprints, replicas, forgeries, etc., so it would seem natural that this would carry over into the playing card collecting market. They can be at times even more rare than the originals due to the fact that law enforcement destroys confiscated counterfeit goods/stamps/bills/coins when they're no longer needed as evidence. The facts that there aren't as many different models of forged decks out there, and by the very nature of the product there's no complied list of what the manufacturer made and who the manufacturers are, makes such collecting even more of a challenge for its devotees. Lastly, the forgeries, even when rare, can be had for a fraction of what the originals would cost at current market value.
As this type of collecting becomes more popular, it will have the unfortunate side effect of spurring more counterfeiters to make more fakes, since it represent an increase in the demand for their product. In some cases, forgeries can even be more sought after than the originals, because the originals are just too prohibitively expensive and hard to obtain, causing people to give up and get the next best thing. Same thing holds true in the art world - some talented forgers' works are as or more popular than the works of the artists they're copying from.