"As Facebook stretches its tentacles into websites other than its own, adding social and friend-making functionality along the way, the company is positioning itself not just as a website but as an essential piece of the Internet itself...
That puts the site in obvious competition with Google and others who are trying to organize the Internet and make it more socially engaging.
Some say a Facebook-led social web will make online browsing more convenient.
As the entire internet becomes more tied with a person's social network, you'll get more recommendations that can help you find web pages you'll enjoy...
Others say the Facebook model gives one company too much power.
"They're holding all of our data. We have to trust them not to sell it to the world," said Ricky S., an app developer who works with Facebook..."
Here's what is wrong in that FaceWeb: Facebook is attempting to become a single center of operations. The main principle which Tim Berners-Lee introduced to Internet and the very reason why WWW became so successful is distribution. Web explicitly avoids to have a single point of control. Is it peer-to-peer or is it a communication through servers, there are usually many duplicating ways to be connected. There is no single database which ties in the Web, there is no center. That's why Web is scalable and dependable, that's what to certain degree ensures Web's neutrality.
Yes, Facebook’ Social Graph is a powerful thing. But as always, a key to success, to a scalable web is not a single center of command, not a single plumbing of the web (which Facebook aims to become), but a distribution, redundancy and the ability to communicate on the same language: communication protocols.
Sure, small cites cannot afford developing their own social graph functionality, they can delegate it to Facebook, but it is better at least to have multiple portals offering such a delegation services, or lending / offering for free standard social graph tools.
Then, the term "semantic web" means something different and much more broad than collecting and borrowing user profiles. I'd refer you to Tim Berners-Lee and to various books about semantic web, but in a couple of words, semantic web it's about ways of attaching standardized tags to web entities, allowing "machines" (web applications, etc.) to obtain meaning (hence "semantic") of those entities.
People as web entities and their social profiles as tags are just a tiny part of semantic web. Tim Berners-Lee initially was talking about web sites as semantic entities, with tags allowing "machines" (web robots) to grasp purpose/area of a particular web site.
Then there was an idea of Web of Things with special unique codes attached to things of a physical world (like electronic devices, or packages in a grocery store, or houses), allowing to uniquely identify and map this physical item to the web. Remember QR-codes? That's what they serve for. I was surprised to find QR code on my mother-in-law's Microsoft Zune HD package.
So, back to our topic: although they are some semantic aspects if what Facebook is trying to do, they use the meaningful term mostly as a buzzword…
An update of October 07, 2010:
So Facebook got Groups. Meh...Months ago they said they knew all about Google's "secret" plans and now they roll out this. It is pretty obvious that the "secret" plans they were talking about is Paul Adams public presentation "The Real Life Social Networks".