I will deliver or meet the buyer within a reasonable distance. This really eliminates the 'sight unseen' purchase. Most of the breeders I spoke with said there were no major differences. I would suggest that Internet marketing offers the same courtesies and services as local or any other marketing. This includes a guarantee of health and support as it is needed.
Internet marketing is really no different than any other method of marketing.
Reputation, a quality product, confidence of the buyer and support are all important. The other side of that is that many people do not know of the sites or domains where what they are looking for is offered. That is slowly changing, more and more people are using the 'net' for their birds and related stuff. Christina Menard had some interesting insights into the differences. On the Internet you do reach more people but you cannot get the same prices you can get through other means.