maintaining a Facebook page has much to do with what kind of employee I want, unless perhaps those "tweets" particularly socially unacceptable.
Unfortunate point you seem to be missing is that HR do not care about "what you need". And maybe due to my increasing age, I can understand their PoV. They do not understand, or they do not believe that it is their job to understand what you and your future co-worker, assistant, slave would be doing while working. I have spent maybe hundreds of precious working hours to explain, if a network team could find time to play a networked FPS, it is a good network team. In short IT definition of work is not compatible to suits' definition of work. HR mainly concerns with turnover rates, costs and business ethics etc.
HR people usually believe that sociable candidates are better that not so sociable ones. So that, regardless of the qualifications related to technical abilities, they are looking for such activities. So a good social networking presence is a better start for any job applicant. Fortunately Linkedin and slashdot are also acceptable as social networking environments for most HR experts.
I do not have many real friends, who has them I do not know...
Living on Earth may be expensive, but it includes an annual free trip around the Sun.