I was helping one of my sons today with a piece of homework, which involved writing an essay addressing the statement "social networking websites have reduced possibilities to form real relationships", or words to that effect. Thinking about it together, one of us came up with the point that in the days of pen pals - arguably a precursor to social networking - people got to 'know' each other remotely, and if/when they met, felt they had a relationship already. This insight seemed, at a stroke, to debunk two points often claimed about social networking sites: that they are somehow uniquely about computers and the internet, and that they are the first instance of attempting to substitute the 'real' for the virtual, as far as relationships are concerned.
My son went on to mention other benefits such as one-to-many conversations and near instant responses, but we both felt the 'pen pal insight' was something of a killer argument against those claiming that real relationships are being killed off. I suspect I might be using it in a professional context before too long.