Amazon list shilling
Did we know that some Amazon lists are made by companies? For example, David Payne is an eBusiness Channel Manager at Viking, and has made over a thousand "So you'd like to..." guides and almost as many Listmania lists on Amazon.
As a result, Viking products show up on almost any memory-related search, and it's got to be helping their sales on the site significantly. There's a vaguely astroturfing feeling to it, but it's clearly not duplicitous or against Amazon's policies. I'm curious to see if any other companies are doing this.