What substitutes for Twitter?

As odd as it may sound, Twitter in many regards is a single point of failure in my network.  In other words, I have no real replacement for it.  Yet I rely upon it fairly heavily as a means of staying connected with people I respect, and whose opinions and expertise I trust – in some cases implicitly.  So when Twitter goes down – as it has right now – it’s a big deal.

In many cases I have no other way to get in contact with people – no email addresses, no instant messaging contacts, no memorized blogs or wiki addresses.  I rely exclusively on access to a single service for much of this information.  In IT terms, there is no redundancy, no fail-over, no data back-up – and that’s very bad practice.

At one point some time ago I spent a week looking for an alternative to the service, and ultimately the conclusion I came to is there are many good services out there – or at least there were before Jaiku and Pounce both met their demise.  However the one crucial element each of them is missing is the human element – the people, the social framework, the network.  The source of information, input, expertise and knowledge; the people I have existing relationships with.

Changing services is one thing – that’s the easy part.  Taking your network with you is an entirely different matter.

Yet once again, Twitter is down, and I’m reminded of how dangerous it is to rely so much on a single service, when all services are destined to experience downtime from time to time.

So the question remains, what substitutes for Twitter?

Update: According to TechCrunch, the Twitter outage was due to the fact it was hacked.