I am going to begin this with a small disclaimer. Pay what you want DOES in fact work if you live someplace small, people will be shamed if they pay nothing, and its a face to face or honor type service where their coworkers and neighbors are watching them. It also DOES work in cases where what you are giving away is a failed product and your only option is to just give it away and hope for the best or just waste time and money invested so far and receive no money at all.
In all other instances it does NOT work.
Number of people you can Google and read about who tried to use this business model properly seems countless.
Radiohead used it for their 2007 album 'In Rainbows'.
Its been written about on major media sites like The Guardian.
Kiss's Gene Simmons is even quoted as having said "Come on in and pay whatever you want.’ Are you on fucking crack? Do you really believe that’s a business model that works?”
Yet I see people keep trying it, with usually wasted time and resources.