I first heard of personal branding over 10 years ago, long before this whole social networking trend took off. The mantra then was to decide how to differentiate yourself and then be consistent. That advice is still being given out today. It's advice well heeded.
In fact, the most important point of a long Knowledge@Wharton article on self branding (link below) is that you really need to brand yourself to get find employment, stay employed or have a successful business as a sole proprietor. These Wharton professors are still saying that you must also be consistent in your branding. Ask yourself these questions: What are you? What differentiates you? What value do you bring? Then, foster that image online and off.
Here's a link to the article - Advertising Yourself: Building a Personal Brand Through Social Networks.