[gocard]

If someone was standing in front of you, and you asked him a question, and after a 30 seconds didn't get a response, would you just stand there, or would you prompt him again to figure out why he didn't answer? Maybe say it louder, because he didn't hear the first time. Or perhaps he's confused, and you can clear that up by asking your question in a different manner. You wouldn't just stand there waiting forever, however.

People begin clicking, typing for the very same reason. You're trying to figure out why a response wasn't given. You click again to make sure that your click registered the first time. If it wasn't the application will now respond. If it was, now you're trying to decipher whether the application is hung or not, or perhaps something did grab focus, like a pop behind, as a commenter suggested.

I guess I don't find this a particularly interesting investigation of human behavior. What's the alternative for the person? Sit there and wait forever?