OMG, WRONG. Wrong, wrong, wrong.
Consider this quote from the AdAge article:
"Websites are important because you own them."
This statement is why the definitive answer to the question "Do we still need websites" is YES. Twitter is down constantly; Facebook can annihilate any Page, no matter how popular, with one mouse-click--and they do. Posterous has been slammed with DOS attacks this week, and my personal blog disappeared for several days when my domain name was declared to be "fraudulent" by eNom. No explanation, just--poof!--blog gone for several days. And back to Facebook--how about how it changes constantly--changes over which you have no control? Or doesn't work the way it's supposed to, such as with the "like" buttons and their notoriously sketchy performance? In theory Facebook is great; in practice, not so much.
And that doesn't even begin to touch stuff like UI, URLs, SEO optimization or any of that nerdy stuff.
Call me a control freak but no WAY would I put all my eggs in the basket of using a website that I have no control over as the main or only hub if I owned a business. Sites like Facebook, Twitter, etc are called "outposts" for a reason--because they're meant to be satellites to your brand's real asset: its website.