The solution needs to allow identities which are "register once, use anywhere" across the web, and portable so that you can migrate to a different identity host/provider/implementation without losing all your accounts. Ideally these identities would also allow you to reveal as much or as little information about yourself as you want, and not force you to reveal some unique property which is correlatable between colluding sites.
Obviously that's not an easy thing to create, and may actually be harder than creating a viable rival to Facebook, but if we don't solve the web ID problem, then governments and corporations are going to "solve" it force us, and we'll all be the worse as a result.
It's a fascinating idea to have some means of identity authentication where the party seeking to authenticate your identity doesn't have enough identity information to connect the dots, and the party providing authentication doesn't even know about the party seeking authentication.
I abandoned my Facebook account many years ago and refuse to set up a new one. As a result, it is difficult for my children to interact with me. They post their lives on Facebook, but they don't open that up to the public. So only specific Facebook accounts get to see what they share. That excludes me.
I have to open myself to Facebook to see their content. Alternatively, they could set up non-Facebook websites and "blog" their lives there. But that is harder than just using Facebook, and gets really hard if you want to keep it viewable only by select people. And then I would have to set up an account on their server to be able to see their content. Multiply that by all the people I would have to set up an account with and it's obviously unworkable pretty quickly.
I still hate Facebook, and refuse to set up an account with them. But I recognize that the alternatives are not pretty.
Edit: typos