We found this article by Nathan Lyle to be most helpful in answering the question…

Do I Really Need a Website? I’ve Already Got a Facebook Page…

Some people, in seeking to keep costs down, will skip building a website for their business and just use a Facebook page. It’s online, it lets you post information and photos, so isn’t that just as good as a website? Nope!
First, let me say that you almost most certainly should have a Facebook page for your business. While there are some exceptions, most businesses can benefit greatly from using social media. The easy-to-see benefits are that it’s free, and lots of people use them. However, if you are relying only on social media, you are leaving yourself open to disaster.
We’ll start with the biggest issue… any of the free services online can “go away” any day. They have no obligation to you to remain open and available. (Remember Geocities and MySpace?) Even if they don’t go away soon, they often change drastically in how they work, and what they allow. Most of them are also very controlled, only allowing you to customize things so much.
Facebook isn’t about you. Neither is Twitter or LinkedIn. You are the resource. These companies need you (lots of yous) to be successful. But, to make money, they just about always need to stuff advertising into everything. They often start off with out it, and then work it in over time. (Facebook and YouTube are two good current examples of this.) This means your presence on their site will be heavily branded in their favor.
The right way to do it is to at the very least have your own domain name. If you absolutely don’t want a website, you can point the domain name to whatever social thing you’re counting on. Even better, however, would be to have at least a very basic website (which lets you have a central branding and resource for contacting information for your clients) and then link from there to any and all of your social presences. Those social pages should also link back to your website.
Think of it as your own personal web… your website is the center, branching out to as many online places as possible. The bigger your web, the bigger your presence and importance for things like search engines. It will be easier for people to find you. And the biggest advantage is that you have a central position that you control, and can adapt the outlying branches as needed. Facebook goes away? No problem, set up something on whatever takes it’s place and link to that.
The take away is that even if you don’t need a website that sells for you, or does other tricks, you should at least have the online equivalent of a business card.