I see nothing wrong with anecdotal "evidence" (per se). As consumers we are swayed by what we see around us. If all of my friends has silver cars I would either buy one to fit in with the crowd or not, to "stand out". In the event that I didn't know anyone with a car, the colour would be less important. I concede that it is folly to assume that one's sample of friends is representative of the wider customer base, that said, they are part of that customer base.