Rules on Review...

HI AuGoNers. since i am fairly new to this hobby and very interested on readding reviews on items.the thing i am a little confuse about is,seem like most of the reviews are good reviews.seem like every one think the itemthey are reviewing worth more then what it cost..is there a rule out there that one can not do a bad review? how come i dont see any review that tell us a certain item is so bad that we should not bother with it?.i am not just talking about the reviews on audiogon.. the 1 on magazines are also included.if any one have any link to a bad review please post it up,so i can see it..thanks