Most have had positive experience renting from owners. I still love to rent from owners, just do your homework ahead of time and be cautious. Even management companies rent homes of private owners and often do not know whether or not the owner is financially solid.
Some of these already mentioned and good ideas: Payment by credit card, checking out the tax records, checking the real estate records to see if the property is for sale, talking with the owner personally, look at how quickly and effectively the owner communcates, see how their availability calendar looks, ask lots of questions, look at reviews! There are still lots of great owners out there with wonderful properties. Renting through VRBO or Home Away offers some extra protections to renters as well. Some owners also offer you contracts from their management companies and payment through their management companies so you have that extra protection, too. Last year when I rented a condo at the beach, I rented through the owner but received a contract from the management company and paid through the management company, so had same protections.
Sandy