I'm not arguing that the communications stay theoretically secure. If there's any processing going on, they clearly don't. What I'm saying is that you break the

I'm not arguing that the communications stay theoretically secure. If there's any processing going on, they clearly don't. What I'm saying is that you break the message up into risk and non-risky parts, and the risky parts (URLs) can be treated differently. That different treatment is very valuable to the vast majority of users that don't care about complete security, but do care about having their systems compromised. Which "betrayal" is worse -- Skype being able to look at messages, or compromised systems? In terms of implementation, it's interesting to think about the design space.