My SO has lots of experience working in businesses selling stuff on-line and while negative comments "out of spite" happened rarely to her, what she often told about is how dishonest employers made workers bribe people so that they cancel/remove their negative reviews. Hearing the stories that I did from her, I no longer treat lack of negative ratings / reviews as a strong quality signal.

EDIT: Oh, and speaking of Amazon, Google and their automated bans, my SO's company's work account got temporarily blocked by Google recently, apparently for the sin of sending several files in quick succession to her boss' account. Apparently "atypical usage" is grounds for a ban now. Fortunately, the account was unlocked few hours later, and I didn't have to make fuss about it here on HN...