Theoretically, technology companies can have employees systematically down-vote all questions that indirectly reveal their products' or services' defects knowing that this would help hide the questions and ultimately prevent the users from posting further questions on Stack Overflow. (Due to the SO banishment algorithm.)
It may have happened to me lately. Of course, I do not have access to the proper data that would allow me to prove this, but recent events made me suspect something along those lines.
Is there a mechanism in place to avoid such situations? That btw. would be impossible to be proven by the "victims" alone!