I have sold puppies online and bought puppies online also. I do talk a LOT to the person before hand - I would do so on the phone and not just through emails.
I actually just sold my baby girl Lexie and she went home today! I was in contact the WHOLE time with her new Mommy as she was flying to her. If you are afraid the dog isn't "real" you could always ask to have the pup photographed in front of a certain object. Something that everyone would have in their home. If they can't do it..then they might not have that pup to be able to do so.
We have bought puppies and I have to say the only time I was ever unhappy was when I bought a dog from overseas. I knew things were not going to go well when communications didn't go well, but at that time I had already sent a deposit.
With us shipping the puppy today...the lady sent her money for her baby girl. I gave her our vet's phone number and put her on the ok that she talk to them list if she wanted to verify the exam time and date. Then I scheduled the flight and gave her the confirmation number for that flight so she could even call to verify if she wanted. Then today we went to take her for her flight. I called the moment I had her airbill number so she could track her online and to verify the time the flight was scheduled to land. Then I sent her a photo of the pup I took on the way to the airport. It was a fast flight and she called me the moment she got her. She LOVED her and said she was beautiful (exactly what I wanted to hear LOL) and her tail was wagging the moment she opened the crate. Today was a wonderful day
Of course we spoke all of the time during this and leading up to the flight!!