A big mistake people do before leaving feedback is checking who else has posted and what. If it's mostly negative, I am not going to say anything positive and vice versa. That's wrong. It's your experience that matters, regardless what the community thinks of it.
I disagree on this. Feedbacks and reputation are not things that work out in isolation. Many users give negative feedback or positive (but mostly negative) based on the proof presented by others and that's how it should work.
A website appears on the forum and are accused by a lot of users of scamming, if I go through the reference provided and consider it valid, I can also drop a negative feedback.
If I had an isolated positive relationship with them, but see overwhelming cases of violation of user agreement with enough evidence to support it, I will refrain from giving a positive feedback. The user could be farming for positive feedbacks to help them look trustworthy and scam more people.