Almost all of my blogging is humor, so when I get the odd comment that doesn't seem to get the joke, it makes me take a closer look to decide if my writing was subpar or if it just was a case of a super-literal person landing on my blog. 

If it's my writing, I can improve but if the person doesn't share my sense of humor, there isn't much to be done other than politely thank them. You can't really debate what's funny! Heh, for all I know their comment was a joke I didn't get!

I do enjoy it when conversations take twists and turns but I admit sometimes I find "hijacking" discussions extremely annoying (this is more of a forums problem than a blog problem).

I agree with Meredith, social media is what you make it. Perhaps I'm being too defensive, but it makes me bristle when people who know I am quite active on Twitter, etc say "Well I can't imagine anyone would find my life interesting". People say/said the same about blogging, Facebook, etc. 

What I'm finding in my own life is the less I fear speaking up and the more confidence I have that yes, I am a person with ideas worth sharing and promoting, the less it bothers me that other people are taking these risks, too.