The halo effect refers to the massive success of the iPod, a dark shadow eclipsing the light of the Mac platform, which can now only be seen dimly around the edges of the iPod fad.
(No, that wasn't serious either. People expect iPod fans to eventually try Macs too. That's the halo effect and I'm all for it. I'm all for iPod success even without that too--it hardly hurts the Mac for Apple to succeed with the iPod. And the halo effect could be even better with IT: eventually if Macs make their job easier and they can find a way to stay useful without fighting MS problems, then sometimes they can pretty much TELL a lot of people--even CEOs--what they're going to get. Macs! Then the halo spreads home when those people--however small a segment--like the Macs they use at work. "Eventually" is the key word in all this!)