Actually they do..
There was a segment on Dateline or 20/20 (cannot remember which) about six months ago about a couple of these firms. They marketed everything from Vodka in a bar to movies in bookstores and on the net. They even hired kids to post positive messages on the net about some anime movie. I will try to find a link to this.
OK, I lied, it was 60 minutes and it was almost a year ago...
http://www.cbsnews.com/stories/2003/10/23/60minutes/main579657.shtml?CMP=ILC-SearchStories