If you have your site parked at a registrar, you can not get into the site to change the index page (unless they give you cpanel rights). So since most registrars do not charge for parking the domains, they can and legally do so, put advertising on those parked domains to help offset their costs and to make a little money. About the only hosts I would avoid would be yahoo, godaddy and 1&1. You can host with me, just PM for the url.