So we're tired of remembering all the log in details for each service we use on the Web. For instance, I'd like to log in everywhere with my Google Account because I use a bunch of services on Google. Others may be spending more time on MySpace and would prefer to log in everywhere with their MySpace account. OpenID allows for that.
Another thing, I want to log in to Facebook and see the pictures that my friends shared with me on MySpace. E.g. Plaxo is doing that in a very consistent way, by integrating many many services under one Plaxo's ambrella. That's maybe an exaggeration but with OAuth everyone can do this.
And so I am also doing that on my free time: playing with OpenID libraries and trying to integrate with other sites using OAuth.
The fact that social networks will be like air motivates me. And the fact that I will be able to login to Facebook with MySpace credentials hints that I am on the right track. Finally when I see services (with a business model behind it) based on OpenID (e.g. RPX), I am really feeling that the whole Web soon will change.