Other (rather nice!) terms for the practice include :
Amazon bombing: Concerted effort to change Amazon sales rankings by simultaneously buying productOf course, we book buyers are really not so naive as to believe all the hype. Or are we?
Sock puppetry: The act of creating a fake online identity to praise, defend or create the illusion of support for one's self, allies or company (New York Times)
Astroturfing: Formal political, advertising, or public relations campaigns seeking to create the impression of being spontaneous "grassroots" behaviour (Wikipedia)
Seeding: Process of placing viral marketing such as videos in forums etc
(Picked up this story from Ellen Whyte's Facebook page.)