The idea isn't a new one, it has been tried in several ways before, including American Airlines requesting $250,000 to fly free for life (program ended in 2004.) So, let's break it down: $599 for a round-trip coach ticket anywhere in the continental United States is high, considering JetBlue has already dropped prices to $100 for many destinations. And what are the chances are the average American is going to be able to fly more than two times in a month or has that much vacation? (Perhaps if they're laid off?)
So, in reality, promoting travel after labor day in the airline's weakest travel time, is probably a good idea. As Bob McAdoo from Avondale Partners told CNN, "This is a way to get people to pay attention, with publicity that doesn't cost the company much. .. They're doing this at a time when there are probably a lot of seats available anyway."
So, win-win, JetBlue -- all that free advertising and a business model that won't lose them any money.