Now, if you're asking this question about why you should get involved in YouTube, your next question will probably be "HOW can I get involved with YouTube"?
First, you will want to learn how to make videos. Second, you will need to know what to do with those videos and how to get them on YouTube. A good resource is Stacia Hopkins' blog and her video training. In her guide for beginners, she explains how to outline an effective script in seven steps (from using a "hook" to closing with a call-to-action), offers recommended products and services related to video marketing, and provides a 10-step video-marketing checklist on what to do to start gaining "massive exposure."
One way you can get out there, is to post a video about your small business in the My Business Story gallery. You can find an "amateur" video of Inkwhy by searching on YouTube for "Inkwhy, Inc." There are also more professional videos that provide advice on how to shoot your own videos, such as the one below.