We too would love to know how to remove a product. I've always been told that you cannot delete them.
So, this is what we do with unneeded products (or libraries)
1) Empty the team - remove all access
2) If appropriate, move any content to another, active product
3) Reuse the product (or library). We rename the product to "Reuse - nnnn". When we get a request to create a new product, we give them one of the products named "Reuse...."
It's a workaround, to be sure.