Sellers are bound by the same laws regardless of whether they sell through a real estate office or through a for sale by owner organization, including the disclosure of defects. There are some sellers that attempt to hide defects, even from their own real estate agent. This type of person is going to attempt to pull the same scam no matter how the home is sold.
In for sale by owner properties, the buyer and the seller are negotiating face-to-face, without a real estate agent to hide behind. That face-to-face negotiation, in addition to a knowledgeable buyer, may keep the seller from trying to put something over on the buyer.