I think that reading these posts a clear picture emerges. It is quite obvious that if it becomes obvious that there are three sorts of complaints. Genuine, trivial, and imaginary. I am certain that there are company's that truly believe that any old thing will do. There are equally customers for whom nothing will ever be good enough. It is a sad truth that these sort of people poison the ground for the rest of us.

If a company sees your track record of consumption and knows that you do complain but do so rarely, reasonably, genuinely, and (and this is very sad) truthfully; you will be taken seriously. If you are prepared to write and say "well done", your letter of "I'm sorry to point out" is taken much more seriously.

With some of the appaling examples cited here, I do not blame companies from keeping track of trouble makers. The danger of course is that it is open to abuse, and can be subjective and judgemental.