That's not exactly true, usually people are already working on distributed systems, and use the failure of centralized systems as an opportunity to point them out.

I personally would greatly fear a decentralized system like Skype, for many reasons.

"Greatly fear" seems hyperbolic. What do you find fearsome about a decentralized Skype?

would do more harm here than good

Such as? I think the adoption of Jabber for IM has worked quite well so far. If Facebook goes down, I don't have to worry about my Google Chat not working.

What problems do you foresee in terms of decentralizing audio/video along with instant messaging?