In some cases why do we use a password at all. There are many times that I register to a site to download something (a pdf in scribd, a sdk in nokia) or to see

In some cases why do we use a password at all. There are many times that I register to a site to download something (a pdf in scribd, a sdk in nokia) or to see a post or a link, in any of this cases I dont care if anyone wants to log in with my username and what are the chances that someone will log in with my username just to change my age or my sex... oh no... I'd rather be exposed to that than remembering another password.