All it takes is one or two or three anecdotal accounts of knowing someone who knows someone who's confessed to receiving something for something and it's off to the conspiracy races.
It actually happened a lot back in the days of print so it's become something like a Sasquatch sighting. Toss in the internet and everyone's in on something and can't be trusted.
This had been discussed to death with the qualifier being getting to know your reviewer and ascertaining if his/her tastes align with yours. It doesn't need to be as deep and wide as some make it out to be. Times change but morals and ethics don't, as much. What used to be verboten is now normal (as a courtesy) so the values needed to do an honest review can still occur.
@larsman +1,
It's so simple a way to do things but there has to be something to complain about.
All the best,
Nonoise