How much should we worry about it? I tend to use it quite a bit in my apps, and with my new interest in AJAX, I don't see that stopping anytime soon. So I know there are people out there that disable it.
How are we supposed to deal with those people? I find it a giant pain in the ass when people complain to me about things that make their life easier, but they refuse to use it. I can understand complaining about a site using ActiveX, because there is a major security hole there, but seriously... Javascript is pretty harmless overall. And if you're worried about pop-ups, get a decent fucking browser. They almost all have a pop-up blocker now.
Thoughts from anyone else??