I've heard of people buying or selling on their own, like FSBO and not had problems. But in a few cases there were major problems. A friend of mine bought a house and afetr the closing called the seller to move in and the seller said "we're not out yet"? Well, it ended up that the buyer didn't get possession of the house until 3 weeks after he paid for it. His contract from Office Depot did not cover "occupancy date"!

Good lesson to learn. Good reason to use a Realtor.