Just read the interesting if somewhat abusive http://500hats.typepad.com/500blogs/2010/02/subscriptions-are-the-new-black.html article.
This tiggered me on the idea that people have problems keeping all those passwords for each site. And many sites could do perfectly without. Thanks to openId and OAuth. Still wrapping my head around the latter, but it sure is interesting!
I guess it will take a decade before lagging web-sites+developers wake up to these techniques... but.. hey... that's a given.