I think the comments on this post are an excellent reason why totally flat threading doesn't work. It's all about the value of the comments - are they there to enhance the original post, or just a way to give Internet trolls somewhere to post (or spam)? Suppose I see a really insightful comment and feel compelled to challenge it or enter into a conversation, without some way to link my comment to another there's no way to maintain a productive 2-way conversation. It just turns into a bunch of random people blurting their thoughts onto a site for no real purpose. (PS: you appear to have a spam problem in your comments)

Why are we logging into websites? I log into my PC, why can't that be enough? Or at least, for people with multiple logins for stuff or kiosks in libraries why can't opening my browser prompt me for a login? Then magic SSL encrypted XML hand waving can make it all work. The details are unimportant, the concept should be "human identifies itself to the computer, human identifies itself to the browser. Browser handles all the other stuff" We can cope with typing in admin passwords in OSX to do certain things after all. Of course then if someone works out your password, your entire online life is compromised... but that's about as important as letting people know the PIN for your VISA card (and you don't do that because it'd be moronic).

I've got a Core2Duo PC under my telly sat inside a HTPC enclosure (which doesn't really mean much apart from the case being black and low power!). The machine runs Ubuntu and XBMC, and also serves as my NAS, samba server, private web server and torrent machine (running torrentfluxb4rt). I've not tested the machine's power consumption, but at night with everything switched off (apart from the server, fridge and assorted clocks, stuff on charge, etc) my entire house draws 0.3kW/h. Switching a light on causes a more noticeable increase than turning the server off. before this my server used to be a Pentium 4 machine which alone drew 160W and gave out enough heat to warm a room! The low power machines are good for specific uses, but if you have one computer left on permanently it tends to get used for everything to help justify its reason for being switched on.