Read about it at Borepatch's place.
In a side note, I haven't stayed at a Marriott since due to their error I was left stranded in the dark on a rainy night in Queens. They not only messed up my room reservation, they refused to call around to see if there was another place nearby that had a room or to let me use their phone and phone book to do so myself. (Yes, I'm ancient, it was pre a cell phone in every pocket days.) A letter of complaint sent to their corporate offices received no response so I decided it was a corporate failing, not due solely to bad management at that establishment.
If you have an early flight out of LaGuardia, don't book at the local Marriott, they aren't reliable.