It is a problem, yeah. But annotation brush works so perfectly and because it is more useful thing for reading science articles I am so happy about it. My conference is over and muViewer was the excellent thing to make it better. I have seen as other people have to bring every day abstract book (~1kg), program of the conference, notepads, list of authors and many other things... and I was only with me eeenote which collect all this stuff inside. And I could annotate and erase all I want and take notes and so on. This was cool!