I've used this site as a breeder advertising resource for over 5 years, and although there has always been a few people who have tried to set up 'scams', the numbers now are overwhelming. This site has become a scammers paradise, and honest people looking to purchase a puppy should know what to look for so they don't get ripped off.
Here are some tips for people who are looking to purchase:
The price is not "too good to believe" That is a sure tip off if the puppies are significantly cheaper than most other ads.
The grammar of the ad is not very good or they use unusual wording (a lot of these scammers are not native English speakers).
Scammers tend to list all their puppies separately...don't know why, they must have lots of excess money from ripping people off.
Call them, if you actually get through, ask them to produce some puppy noises in the background. If they can't they don't have any dogs there. Ask them to personally email you scanned images of certified pedigrees (breeders do not publish these on the web, so they won't be stolen). If they can not email you a scanned image of a certified pedigree(and it should have a watermark of the kennel's name across it) they don't have it. They are scammers, dog owners who paid thousands for their dogs have their dog's pedigrees!
If there is a discrepancy between phone numbers, where they list one on their ad and a different one at a website they have created, don't trust them.
Scammers are creating very convincing separate websites now. I just visited one that was trying to sell one of my own puppies, with my picture and even the name we gave our puppy. Now my puppy pictures will all have watermarks on them. Visit many websites, if you see pictures of the same puppies being used, someone is stealing them. Scammers have even stolen my family pictures of my children playing with the dogs and published it as their own. It really creeps my kids out, to say the least.
Finally, call and talk to many breeders, ask them questions about breeding and for details that only a real breeder will know. I say call, because if you email, the scammer can just google your answer, but on the phone you will know if they really don't know what they are talking about. The more real breeders you talk to, the better able you will be to recognize when you are talking to someone who doesn't really know anything about selling puppies, they only know what other breeders have published.