Neville,
The coin deal being discussed here was a deal where you buy a limited edition coin directly from the US Mint and then sell it directly to a coin dealer and they would pay you more than you paid. The reason the dealer couldn’t buy it themselves is because there was a limit of one per customer from the Mint.
People feel it was a scam because instead of selling the coin to the dealer, you could have sold it on ebay for more than the dealer was offering, so they claim that the dealer wasn’t being honest.