It doesn't bother me. The way I see it, FB is quite public. It's like being out in the town square. You want privacy, you have to be deliberate about it [that is, use the messaging function].
And I guess I don't really see the point of trying to be private on someone's wall, where people can see it by just visiting their profile.
The whole point of FB is to encourage interaction. With most things going into the live/news feeds, it achieves that end.
Just yesterday a couple friends were doing a wall-to-wall conversation and a couple of us glommed on and it was really funny. It was a total hijacking [or guano as we call it here, and no, the OP totally didn't mind!