I think one reason it would be awkward is because of what Phathead said...
I don't say anything I am embarrassed or ashamed of, so I really have nothing to hide, but because neither of us are actually admitted to a school yet (unless you are Phathead?) I personally don't want anyone reading my posts and hating me just because of something they took the wrong way or anything like that.
I know it sounds paranoid and far fetched, but I am very cautious person... I was raised that way, and I think it's served me well so far. I would have no problem discussing my true beliefs and showing my true personality to an adcom, but I think the internet and written words in general leave a lot of be desired about knowing how a person really is.
Sometimes I come back and re-read my posts and think that I sound like a really immature little ditsy girl or something... even though what I wrote at the time didn't come out the way I meant it for example.
I also think sometimes it is awkward because you have NO clue who the person is but they're like OH HEY so and so... don't I know you from somewhere? Like I said in previous posts... this has happened to me at very strange and inappropriate times because of facebook.