All the respect in the world for Chael Sonnen. Dude has balls of steel.
Why do people keep saying this? Sonnen was offered a fight where he had literally nothing to lose and everything to gain. Best case scenario for him would be he beats Jones and becomes LHW champion, makes a shit ton of money, and has his popularity/legacy/standing in MMA absolutely skyrocket. Worst case scenario is he collects a quick and hefty paycheck and loses a fight that nobody expects him to win anyway that has no impact whatsoever on his standing or how people perceive him as a fighter.
No balls necessary, anybody with a brain would have done the same in Sonnen's position.