This is a serious problem. My wife goes to Amazon and just buys the top seller of whatever she's looking for(even if its from a no name marketplace seller). I don't think she realizes people can game this system.
Most people I've spoken to don't even realize Amazon is a "marketplace" that has multiple sellers.
Until 2010ish, I thought that Amazon sold all of their listed items and that I had to specifically choose "New & Used" from other sellers to purchase an item from someone else.