Sunday night, I was on a delta Md80 from ATL-DAB. We were taxiing out from the gate in Atlanta, had just pushed back and a couple minutes later, had to go back to the gate. Two big (strong) guys walked on, and grabbed this guy out of his seat and escorted him off the plane. The flight attendant, sitting next to me, said that she wasn't sure exactly what the reason was, but that he had been doing some suspicious stuff, and saying things to the people sitting next to them that made them feel the safety of the flight was in jeopardy. We never received an official announcement on the PA, however, once we taxied out again, the Captain came on the PA and thanked us for our patience and said, "sorry we had that little problem with a passenger, but we don't need people like that on our airplanes anymore these days, so we were doing it for the safety of our flight." It was pretty interesting. It was Delta flight # 2027, Sept 8.