Not that anybody really claims to know, but there's some thinking that the Skype outage was caused by some failure of the Distributed Hash Tables that Skype Supernodes apparently maintain. Some say "this is normally very slow and done over UDP," so restoration, even once the problem is identified, will take some time. So even as the ability to send instant messages and set up voice sessions is restored, other niceties, such as correct "presence" information, might take a little longer. The immediate problem, some say, is that if a Skype client cannot find a Supernode (and I am not a techie, but understand a DHT corruption would have something very serious to do with that sort of failure mode, then even if a client is authenticated by a central server, the user would not be able to get onto the Skype network.
All I know is that this failure mode would explain why I can communicate using text, and send audio, but my presence shows as "offline," when I am "online." I will test a live conversation tomorrow morning and see what happens.
This is a crisis management professional's dream: when your client is getting lots of bad press, some other bigger event occurs to overshadow it. So Skype now is sucking all the oxygen out of the "I'm mad my VoIP doesn't work" room.
