Originally posted by jimr-pdx An issue I mentioned at dyxum in my minolta days - a poor lens copy can be sold on the forum and then get panned more than once while a great copy gets just one (high) review. Again this is something to factor in as a reader, not necessarily a fudge factor that the database should calculate for us.
But both problems (yours and the one Transit cites of a low score) also exist at the high end of the scale. People get a good copy, rate it at 10, then later sell it with the new buyers repeating the rating. I've seen lenses sold more than once here. Also, many people rate a lens right after they get it and the new toy may cloud their judgement, not to mention problems may not show up right away.
Another point not mentioned is many times, a person will be vocal complaining about something they don't like, while remaining quite about something that is satisfactory or even stellar. Nor are people always fair in their ratings. I've seen reviews on Amazon where someone gives something a 1 rating that arrived dead in the box, with no word on whether the replacement was satisfactory or not.
For those reasons, no rating system is perfect and people should learn to read them with those possibilities in mind.