Another good thread! I have lost friends through the PhD - they (wrongly) made the assumption that I wanted to just socialise with PhD types and academics, and just put the barriers up themselves. i never indicated anything of the sort. Even my own Mum, who I normally get on well with, often trots out the "Ooh, I feel I can;t talk to you normaly anymore since you becasme a Dr." line, especialy when she's trying to win an argument!
I also got sick of the "oh, off to another conference? Bloody easy life!" - er, no it wasn't actually. In addition to the stress of presenting I didn't like being away from home and partner.
It does annoy me when people don't seem to recognise it for the hard endeavour it is...