You can't blame Big John tonight... in the second, he let Wand have a try to get the choke but Silva did nothing to improve the position and get the choke, Sonnen was obviously not in danger of being submitted... later in the 2nd and in the 3rd round, Sonnen kept trying to change position to GnP or go for the submission...
The ref's job is not to guarantee an entertaining fight... he stands fighters up when they are not advancing position or stalling... MMA can often be a strategic sport on the ground, and just because fans are booing, does not mean that the ref needs to intervene.