For example, if you do not disclose that there is dryrot around the door frame and the buyer finds it after the sale, he could sue you for not disclosing. If you're a doctor, you might say "I don't even know what dry rot is, so how could I know my house has it?" The judge might believe the doctor. But a contractor or a professional -- not so easy to say you didn't know it was there.
Bottom line: no matter what your profession, DISCLOSE anything you know that is a problem/flaw with your property so it doesn't come back to bite you later.
This is a great question, I recently had a seller who is employed by the vriendly neighborhood telephone/television/internet company disclose that he is a Low Voltage Wiring Technician. An unrelated answer on the same topic would be to make sure that form is filled out completely, the majority of real estate transaction related lawsuits stem from what is or more often, is not disclosed.