There are two definitions of "socialising": the one I and probably you use, which is along the lines of "participating in activities involving acquaintances and friends in order to fulfill one's need for company, to make said activities more enjoyable, and to meet people who may become of use for future friendship, love and/or business".
Facebook is behind a growing use of the alternative defintion, however, which is "any one or more of various rituals involving other people whose purpose is to destroy all or part of a person's identity as an individual and replace it with a group identity. Rituals may include but are not limited to: self-harm through excessive drinking, pursuit of members of the relevant sex who hold absolutely no interest to the individual, meaningless sexual intercourse, listening to boring people talk nonsense at business seminars, and participating in irrelevant 'team-building activities'."
Society, as in the thing that Thatcher prematurely declared dead (would that it had been), much prefers the second definition. Rituals mean predictability, group identity means you can pull one string and make an entire population dance. And Facebook is making it easier than it ever has been. Your identity on Facebook basically consists entirely of pictures of what you've been doing with groups; your status depends on how many other people you've given up a part of your identity to; the word "friend" is redefined from the vague and opaque "someone whose company you enjoy" to the more easily recordable "someone whose invitation you couldn't think of a good reason to turn down".
Friendship is an emotional relationship that is essentially random and indefinable. That makes it useless to advertisers and bureaucrats. Facebook Friendship is much easier: it's "B is A's friend, and I am A's friend, and I went to C and did D with B at 9:12pm Friday morning (click here for 30 images as proof), therefore B is my friend." This is more open, more transparent, more conducive to a prosperous and stable society. It's a great improvement on the old 'friendship'. Unless you have a soul, of course.