(For those in the know - I'm not actually going to go into specifics but, yes, it is about that)
It always amazes me just how much people think they know about other people. We assume that we know friends or family and then all of a sudden (or slowly and painfully over a long period of time) something comes along that proves that we don't know these people in the slightest.
And why is it that it's always something unpleasant that gives us the wake up call. Why is it that you hear people say 'I thought I knew so-and -so but he was wearing my knickers all the time' (that is not a real event, just an illustration). You never hear, 'I though I knew so-and-so but he was helping out at the old peoples home on the quiet all the time'. Maybe it's coz people are generally unpleasant more often.
I try not to fall into these assumption because half the time, I don't even know myself - let alone expect other people to know me! But still, human nature (or stupidity depending on your outlook) never fails to surprise me.
And then there are situations where, when you stop and think about it, it's not a surprise at all. You'd hoped and given the benefit of the doubt but actually, it doesn't surprise you.