It seems that the line has been blurred between life and life on the net. I can't help but think that people who devote their time and money to create plush lives in Secondlife or spend hours upon hours gaming, have no REAL life! The interaction that one gets from the internet is in no way comparable to that of physical human contact. It's convenient but no substitute.
Social Networking sites have their place and utility but (call me old fashioned) i think that the only way to build confidence and enhance your social skills, is through talking with others without sitting in front a computer.
People can become zombies by just staring at a screen or lose all touch with reality and become incapable of interacting with others if its not through some virtual world. That is not what i want for the future. My apprehension is not about the games or networks themselves, only about the degree to which some will take this intangible "world". Although it creates a social stage for kids and adults alike who may or may not behave in the same manner as they do on the internet, it can also be detrimental to their development of self. If used in moderation and not at the expense of building real relationships, these sites are ultimately useful and extremely powerful.
I am a user of both Facebook and Myspace, and i like the community and what it has to offer... but i do not use it in lieu of physically seeing my friends or family.