There's been articles on this, but I thought it was worth reviewing. When I started my Facebook page last year to begin to promote my comic, I thought of it as "this will be good enough until I get my website up". Due to a variety of factors, my website kept getting put on hold, while my Facebook page flourished. I still don't have a website, and I see the Facebook page as central now. This is the shift. The old website model for promotion is fading while social media and apps are emerging as the dominant model. Part of the reason for this is convenience and the growing ubiquity of smartphones. It takes too much time to navigate through a ton of website addresses that you want to follow, now that you have Twitter, Facebook, Tumblr, Amazon, dedicated apps, and their brethren. Point and click, and you're there. Commenting, posting, sharing- all immediate. And more and more you don't need a million separate sign in accounts and passwords - Twitter or Facebook will do. Even webcomic creators are fleeing their own sites to rely on webcomic social sites like Drunk Dunk and InkOutbreak.
Smartphones are the future of media because everyone will have one and they will take them everywhere. Websites are just not convenient for smartphones. Social media and apps are. Lots of comics are switching to the new model, but some new entrants I see are still trying the old model, with a website as the center of their work. These sites are harder to find and how many readers will they reach? With Facebook you can sell and promote anything on your site. There's issues with Facebook for sure, but if reaching potential readers is your goal, then social media is where the efforts need to go. The question is how many do you use - it can quickly get time consuming.
I'll still do a website because they have their uses, but I'm not going to worry about the complexities of Wordpress. Google Blogger will probably be just fine and you can still have a dedicated url. The benefit of the website is that you can share more information and share it how you want to. Facebook is still limited in that aspect.
On a side note, I'm hoping Absolute Write starts allowing users to sign in with Twitter and Facebook. One less password and it makes it easier for the writing community to connect. I think if it wants to survive, it will have to adapt.