The story is posted somewhere on flyertalk I think; essentially he (Mr. Pillows) was assigned seat 1A and someone was sitting in 1A when Mr. Pillows boarded. Mr. Pillows asked the ground or flight crew that that someone be moved to another seat so Mr. Pillows could take his assigned seat, a very reasonable request. He later discovered that the someone that was moved was Tilton, then CEO of United.

So Tilton took a seat that was not his assigned seat and he was relocated by the flight or ground crew (don't remember which) so Mr. Pillows could have his assigned seat. But 1A was always Mr. Pillows' assigned seat on that flight; he didn't just board and demand a seat that wasn't his and kick the CEO out of it.