Stuart Butterfield makes a point I really should have made clear, that while social software could impact politics, its applicability is everywhere people are, which also implies the impracticality of precise definition.  He goes on to define it by devices;

So, what is social software? By me, it is software that people use to interact with other people, employing some combination of the following five devices:

• Identity
• Presence
• Relationships
• Conversations
• Groups

Conversations can be real-time or asynchronous. Relationships can be as simple as “contacts” or can be more subtle. There's been relatively little group stuff (yet).

Andrew Wooldridge adds

• Reputation 
• Sharing

[Ross Mayfield's Weblog]

I'm starting to really get off on this notion of social software.  In fact - the more and more I think about it - the better it feels.  Stewert Butterfield also has a link to eyebees - which looks cool.  That's two links in Vancouver in one day!

Here's a question: "Why WOULDN'T social software be everywhere?"  Or put the other way "Why should software NOT be social?"