1) Dana White (and Lorenzo Fertitta and anyone else who makes the decisions that we don't know about). If you added up the total blame of numbers 2, 3, 4 and 5 on this list and then compared it with #1, the proportions would be absurd. It'd probably look something like this, thanks random day-trading ad that happened to be the first image on Google's search:
I like the little sparkle that guy put on the bottom. It really makes it stand out.
There are a lot of reasons why this is the fault of the UFC brass, but the main one is really simple: they're the ones who cancelled the event. Now perhaps in part of the attempted negotiations with Jones and his camp, they made it clear to him that they were going to cancel the event if he didn't fight. Again, though, that little bit of blackmail isn't Jones' problem or fault. Jones is not paid to look after the well-being of other fighters. The head honchos were the ones who made this decision and the blame lies squarely on them.
It is their fault that they've been rolling the dice with paper-thin cards held together with spit and bubblegum. It caught up to them in UFC 147 with a PPV buyrate reported to be only 140,000. It caught up to them in declining ratings on Fox, as the much maligned "#1 contender's bout" between Shogun and Vera drew the same 2.4 million as UFC on Fox 3 did (the Diaz vs. Miller card) - half of the numbers that tuned in for Fox 2 (Evans vs. Davis), which in turn was a drop-off from the 5.7 million that JDS/Cain did on the premiere. I've been harping on this for months, as a matter of fact.
UFC 151 was being maligned as one of the worst cards of the year with the exception of the Jones/Hendo tilt, and the reason for that is because the UFC has spread itself too damn thin. There is a small segment of the population that cares about this and will watch everything. There's another slightly larger segment that will watch big names, stars and big cards. That second portion doesn't give the slightest damn about seeing Jay Hieron, Eddie Yagin, Thiago Tavares, John Lineker and Yasuhiro Uru####ani on something they're spending 60 bucks on. They don't care that the FX prelims have Jeff Hougland, Tim Means, Abel Trujillo and Henry Martinez. When you overreach, sometimes you get burned, and the UFC got burned badly by putting on a card they couldn't sell because there was no one of interest on it save one fight.
This has been a criticism that Dana himself has leveled against boxing before: the one-fight card. But the UFC has gone and done it and all of a sudden, they're coming to terms with the risk/reward ratio of such things. Imagine if you would, the following scenario: current middleweight champion Sergio Martinez is scheduled to face Julio Cesar Chavez Jr three weeks from now. In two weeks, JCC breaks his hand and pulls out of the fight. Why would Martinez be obligated to take a fight against Jr. (light) middleweight #2 Miguel Cotto, who's fresh off his loss to Mayweather? It's an absurd notion. When you make a one-fight card, as this PPV was, and the fight gets monkey-wrenched by injury, that's your fault for setting yourself up this way.
The behavior of Dana was especially saddening, and in some ways appalling. Again, Jones owes them nothing beyond what he is required to give. The power that the UFC wields with its monopoly right now is enormous, and they're used to people doing what they're told. However, Jones stood his ground as he is within his rights to do, and Dana flew off the handle at Jones and his team. His continued bashing of Jackson as a "f*cking sport killer" is sad and also misplaced, as Dana continues to hand out Fight, Sub and KO of the night bonuses to Jackson fighters with regularity.
I'll close with this solid quote by Rainer Lee:
White is doing a hell of a thing, deflecting blame onto Jones and his camp like this, obscuring the fact that this is an unprecedented move for the UFC because UFC cards right now are shallow to an unprecedented degree.
As for the undercard fighters, there are two people they should be looking to before they look to Jones for responsibility: 1. themselves and the extent to which they are a draw in the sport, and 2. Dana White, who has shown very little faith in their ability to hold the show together. Jones doesn't owe money to the undercard fighters. The UFC does.
To sum up what became a massive post exceeding two-thousand words. There are many people you can blame for UFC 151 being cancelled. The only correct answer is Dana White and the rest of the UFC brass, as they're the ones that set this up and they're the ones that pulled the trigger. You can rightfully be made at Jon Jones that he isn't fighting next weekend, but there's no call for him to take the blame for the fall of the entire card.
He's responsible for himself, not the organization as a whole.