You mention how companies hate to lose control of their marketing. True. Yet, the online community and fan base thrives on the spontaneous comments and engagement of their customers. It's up to the companies to get involved in the discussion, but trying to infuse the "company line" makes the dialogue stilted and self-serving, and therefore,ultimately unsuccessful.

I think it is important, as you mentioned, to ask yourself the question: Who needs to know about me? I would also add to that two words...And why? Looking for a job isn't what it used to be. But the web gives you the opportunity to establish your personal brand and then "try it out", learn from any mistakes , and modify as needed. I have friends who go at this little by little, but it really takes an all out effort. The upshot is that it not only gives you a better shot at finding the right position, but also gives you a sense of empowerment.