This makes no sense. Say for instance this is a very small issue that happens with 0.5% of truck owners. What are the chances that Consumer Reports received a problem vehicle? 0.5% of 700,000 trucks sold last year alone is still 3,500 people with an issue. All of their complaints are invalid because CR didn't report an issue?
From what I have read people aren't saying that all GM trucks shake, they are merely giving people a heads up that it is a known issue for which GM has an apathetic attitude. Most of the complaints are that GM/dealerships either:
A) refuse to acknowledge the problem (thus causing people to visit forums to see if others are having the same issue)
B) cannot determine a fix for the problem (thus causing people to post if anyone else has had successful repairs)
C) force you to deal with the problem via outside sources (thus causing people to file complaints, post anywhere they can, etc)
Should people base their purchase on an online forum? - No. But should they completely disregard an entire (or multiple) threads just because the posters are anonymous? - Absolutely not.