[Roth]

I think the proper etiquite is that you give at least a 10 minute warning before you have to leave. However, it is also okay to leave immediately if you explain that something came up and you have to go. I have no real issue with this kind of thing as long as someone is respectful and takes into account the other people in the group. If you at least attempt to show respect to group members there is no way I could be angry.