The easiest way to understand what the next stage of the web will be
like is to take a deep look at Facebook.
Zuckerberg got it right. He (they) managed to attract users and build
a web within the web because he solved the two most critical pending
issues:

1. Structured-ness
2. Identity

Facebook tackled structuredness by simplifying the problem first.
Instead of trying to model "all the possible things" that exist on the
web, they chose to structure the 20% that generates 80% of the value (
people, events, relations, etc ) in the activity that was most
unattended. ( social interaction ). They may have started aiming for
something simpler, but I am sure they figured this out sooner rather
than later. The graph! They were hosting the famous goddam graph
within the web!

Identity was a consequence of getting structured-ness right. Plus, it
was easily achievable, enforcable and distributable within a walled
garden.

Notice that this is all they did. Fix two issues. With that in place,
users and developers simply filled in the blanks.

Now the blue empire is starting to piggyback our browsing activity to
bring the whole web inside of their framework via a set of protocols
and APIs ( opengraph, stream, likes, connect ). This is natural, and
smart. It may sound terrifying to some, but it is actually good for
all of us.

Why?

Well, because the biggest barrier was never technical. It was our
perception of how the web was supposed to be. People got it wrong and
steering the ship proved to be harder than expected. Facebook is
kindly teaching us to "expect" single sign on, to "demand" a portable
graph of friends; In short: to dissociate the data from the container.

Developers are slowly figuring it out now. They are realizing that
there has always been built-in structured-ness in the web and that
they were somehow misled to believing that things were hard. In fact,
they are even simpler than Facebook puts it.

The identity part, on the other hand, has not always been there. But
it is finally crystallizing after several experiments ( OpenID, OAuth,
etc ).

You will soon make a "record" for yourself in this giant database, and
it will all start making sense ;)

Structured-ness and Identity.
The two new features that the web will massively roll-out starting 2011:

Linked Data + WebID