To date, I have purchased two stallions and four mares via online ads. Only two of my miniatures where purchased locally and were seen before I wanted to purchase. I have learned to ask DETAILED questions and if they aren't willing to answer any and all questions that you have - DO NOT BUY! Also, if you get conflicting answers - RUN!
I have never had a bad experience and have never asked for videos. I ask for multiple pictures of left side, right side, top of the horse, bottom of the horse, back side, front side, bite, leg photos, hoof photos and head photos.
I always go to people who I feel comfortable talking with and that I feel are reputable and are willing to take the time to present the horse to me and fully answer and questions I have.
I have yet to sell a horse (I can't seem to let anyone go) but when I do offer one up for sale, I will be giving TONS of pictures and video as well. I want them to be happy with the service they get from me whether or not they buy the horse. Word of mouth travels much faster!