[AceJohnny]

Actually, from talking with the OneSocialWeb [1] and BuddyCloud [2] guys, I understood that Android phones have a really sophisticated "always connected" philosophy. The main CPU can go into deep sleep and the phone still maintains a persistent data connection, waking up the CPU on incoming data. That's for the low-level IP stuff. TCP-over-GSM really sucks your battery.

XMPP doesn't (yet) have a standardized way of filtering data. Using Privacy Lists is a workable hack. Google implemented their own thing (using Protocol Buffers [3] to replace XML-on-the-wire, instead of gzipping as the XSF recommends). Process One has their own system as well for OneTeam [4].

The future ideal is to use SIFT [5], but it is still experimental and as far as I know, only Prosody [6] has partially implemented it.

[1] http://onesocialweb.org/ [2] http://buddycloud.com/ [3] http://code.google.com/p/protobuf/ [4] http://www.process-one.net/en/solutions/oneteam_iphone/ [5] http://xmpp.org/extensions/xep-0273.html [6] http://prosody.im/ (dammit, how do I embed URLs in the reply?)