"We promote your book, and earn $4 from every book sold."
At POD prices that is probably either a pricy book or very little profit left? The site is also littered with typos and very poor grammar--never inspiring. My bet is you buy 5 or your own book, pay to send them to his 'store' and don't sell them. Where are their customers coming from? And that doesn't even touch the idea of paying a monthly 'subscription' to list with them.
Just my take on it.