LinkedIn is a great professional network, as you know, that you can become an 'expert' in your field by answering questions for people on the site. Potential clients may review your profile / online resume to qualify you as a legit professional by reading your experience and testimonials. The conversion rate on this is higher than Facebook but also pretty low when compared to day-to-day sales. However, a conversion on LinkedIn has the highest worth in my opinion.

Twitter is the wildfire of Social Media. You say a few things, or write a few great articles, and soon your name is tossed around in meetings. Interaction and continued communication on this is priority as it can send endless leads to your company. But, that being said, the quality fluctuates. Most leads probably result in smaller projects. But a handful of small projects equals one large project from a financial standpoint right?

So you really have to have a sliding scale in my opinion. In short:

Facebook is nice to have but serves no true purpose for a company in my opinion (unless you devote a great deal of time in separating the benefits to your clients that sign up for this against your other networks or sites).

LinkedIn is key to future growth. Conversion is lower but project size and quality is by far the greatest.

Twitter is essential. It is rapid fire. A few well placed comments or mentions can bring in a lot of traffic to your company website and generate leads. But the leads are, typically, on the lower end of the project scale.

As always, thanks for the mention and link! The Twitter link doesn't work Make sure to include the http:// in all links or your domain thinks it is an internal page.