Comment Inserts (Score 5, Interesting) 130
Another common thing they do is include notes with product that basically say "leave us a 5 star review and we'll send you a $X value amazon gift card".
For cheap items plenty of people end up dropping their 5 star review expecting to get a card mailed to them for often the same value as the item.
Its always funny when you see reviews that say EDIT - Never received my card.