Leaving bad reviews?

[GoldfishMan]

Thanks for adding, Dettol. All good points, but I have to differ on this one:
"Do they write exclusively for one shop or operator"
I wouldn't put too much weight on this point, simply because we humans are creatures of habit. A punter might like to frequent a particular shop because it is more convenient for him, or he just likes that place. Doesn't mean he's suss. I have some guys in my whitelist and greylist that never write anything on other shops, just the one shop they always go to.
I'm also personally guilty of always frequenting only a handful of shops, so I know this happens.