We really need (and will inevitably get) an open, distributed protocol for status updates. It's insane for everything to be routed through one (or 2, or 3) companies.
Well theres statusnet: http://status.net/ . Which I assume would be trivial to sync using pubsubhubbub or wave-style xmpp extensions.
Edit: wiki says they already support this: "Supports Federation, which provides the ability to subscribe to notices by users on a remote service through the OpenMicroBlogging protocol."
There are theoretical lower bounds on the amount of heat generated by the kind of information processing that Google does, and this heat needs to come from energy sources, which are growing more scarce as software/bandwidth/disk capacity/CPU speed grows. Google is the largest non-manufacturing electricity buyer in the world and would never fit in any bedroom :)
Only if you've protected your profile/using private messages. I regularly get @replied by people who I don't follow, and I don't particularly want to lose those messages, so it's probably not a realistic way of stopping spam (although it would certainly be effective).