We have a site on Odoo 8. The shop works well at http://cferalma.com/shop.
But it is only a catalog. Users can't buy on this site. No "add to cart" button, nowhere.
But sometimes (often), sale order are created for the public user in the sales. We don't want these sale orders.
I will publish below our solution for this problem. May be it could help somebody.
Thanks to comment.