When Romo was suddenly ruled out leading up to a Week 17 game in 2013 I was able to place a wager at one book on Philadelphia to cover the spread as soon as I heard the news, before the game was pulled and later re-posted (at a much different number for obvious reasons). I'd found out about Romo's status on ESPN and figured it was OK since the book should've been quicker to respond to what had become widely available public information - plus, it's not like whoever had taken Dallas earlier in the week would be offered the more favorable Cowboys line when it was re-posted. Not the same as going past post, but a similar situation in the form of an error on the book's part. Of course Dallas managed to cover the original line so that Eagles ticket lost anyway. Interesting, though, to see a book get on its moral high horse when the tables are turned.
If they kept their lines right and paid attention to the news, these circumstances would never come into play. Occasional human error will always be part of the deal, but it's on bettors to be astute and take advantage of a rare edge when they can get one. While every book reserves the right to ban anyone anytime, it sounds to me like some of that vitriol should've been reserved for whoever let that ticket go through rather than the guy who was observant enough to exploit it.
I'm relatively new to this world, but it seems like common sense. If your local Shell station accidentally posts gas at $.350 a gallon instead of $3.50 a gallon, do you go inside and tell the clerk? No, you fill up your tank as fast as you can and drive away with a smile. You've overpaid for long enough and you know you'll have to again, so you simply enjoy the cards being in your favor while you can. And if they ban you, there's always a Chevron and a 76 right around the corner.