I have a friend that never gives me warning of when she is coming. Sometimes she will call from the cell phone while she is driving down the street, but thats usually it. There have even been a couple of times when she has woken me up with the doorbell (the kids and I sleep in sometimes when we've been up late.) It doesn't bother me from her because she is a really good firend and I don't care if I'm in my pj's and my house is a wreck.
But dh's grandmother tends to just show up at our door too and it is almost always while I am cooking dinner. She ends up talking to us all while we eat, but won't join us for dinner. It is a little uncomfortable to me. Oh well, I guess its better than not seeing her at all.