I never cut NBC any slack, but they've earned it here. The show started out on Wednesday nights. They gave it a trial on Monday night behind the network's biggest hit (Heroes at the time, what a joke) in order to get it additional exposure. People just wouldn't watch. From a ratings perspective, there is no reason it shouldn't have been canceled after season 1. Say what you will- but they gave it a full year to catch on and some advertising exposure.
Critics raved, so they gave it another chance. On Fridays, where it didn't have to do well. The show's loyal audience needed to watch it on Fridays, and it would be fine. Well, the numbers were still bad.
So then they made a revolutionary deal with DTV to keep it alive. After 2 years, it was obvious it was never going to be a moneymaker for the network. But they loved the show and wanted to keep it. So they cut DirecTV into the deal as a way to keep it alive. Numbers were still terrible. But they managed to work a deal with DTV for 2 more years.
5 seasons (4 more than it probably should have had) and an unheard of network-sharing deal. They have to get some props for that, when no other struggling show has gotten near that.
There is only so long that you can hold onto "the audience will get bigger if you give it a chance" theory. After 2 years, there was no chance it would get bigger. You can only hold onto a money pit for so long.
NBC deserves to be savaged for a lot of things, but their treatment of this show honestly isn't one of them.