I recall reading a report that several eBay vendors had been targeted by blackmail reviewers, so I would want vendors to have some recourse, especially if you find that buyer X has given several vendors terrible reviews.

     I only make freebies, so I don't have a vested interest myself, but I can see two sides to this.  My gallery is essentially a freebie catalog, and I allow comments, but I reserve the right to respond.
     If a criticism is constructive, I may well thank the reviewer;  if it's apparent that the reviewer is snarky and/or incompetent, then I would want to be able to contest the point.

     I like the current system, in which I may review an item if I'm particularly happy/unhappy with it, and the vendor can respond.
     If I paid for an item, I'd be kinda torqued if some socialista required me to review it.  And don't send me a reminder.  I get enough spam already.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5