A blog isn’t you. it’s “you, edited you”
Everything you write, thought out, edited, revised published, circular, cryptic — its the ‘you’ you’re willing to present. The meticulous arrangement of words and ideas to say one thing, and suggest another — offering a disclaimer, context, and subtext to every concept discussed.
Because of the nature of this ‘arena’, some ‘personal’ things can never come out in a blog. BUT, as your friend/colleague pointed out, other things come out more easily (and perhaps only) in a blog, as you can handcraft the way the material is presented, and can go back and edit everything before anyone reads it.