The latest comes from Ted Wallingford who says he is dropping Skype because it slows his Macbook down too much. I think the following is even more significant:
There you go. Switching cost is proportional to the size of my contact list, just as it is for IM. If I have a small contact list, or my important contacts are already also using the next “free” Skype clone, then switching cost is not very high.