Will Websites be the Social Networks of the Future?

I was thinking about this issue over the past few days, so I decided to put my ideas into written words. I am not sure if they will make sense, but let’s try.
Assumption One: Most people will want/need to have an online presence in the future
Notice that “future” here might be 10 or 20 years, we can’t know for sure. The assumption just requires this to happen somewhere in the future. It doesn’t matter when.
So the first assumption is basically stating that some day, most people will need to be on the web. This includes kids, teenagers, students, professionals, companies, institutions and so on. Different people will have different reasons to have an online presence, but most will have at least one reason to do so.
Assumption Two: People like to own their stuff
One of the problems with most social sites today is the fact that the users don’t own the sites. They don’t even own the individual contributions that they make.
Suppose you have a Twitter account where you publish hundreds of quick tips on a certain topic. After one year, if you wanted to export all those tips and publish them on your site, you wouldn’t be able to. Your account is owned by Twitter. On top of that, they also have the right to shut you down any time. Here is a quote from their Terms of Service:

We reserve the right to modify or terminate the Twitter.com service for any reason, without notice at any time

People like to own their stuff. If there was a checkbox saying “Do you want to own your Tweets?” when you were creating a Twitter account, I am pretty sure most people would check “Yes.”
Assumption Three: Technology will evolve, bringing social features to any website
If people like to own their stuff, how come they subject themselves to the terms of social sites like MySpace, Facebook and Twitter? How come they put work into something that they don’t own?
They do that because there are no alternatives. Yet.
If you want to connect with your school friends today, for example, you will inevitably need to join a social networking site.
But what if you could have all those features inside your own site and still own all the stuff that you would put online? For example, what if you could add micro blogging features to your website and send messages back and forth like you do on Twitter? What if you could create communities and groups of interests like you do on Facebook, but based on your own website?
I am not sure how we will accomplish that, but it could work.
The social aspect will be the same, the only difference is that it will be based on a scattered network of websites instead of on a single website with different user accounts.
What do you think?