In any case, I don't think that trade shows really matter much any more. Back in the early days of microcomputers (back when we still called them that), trade shows were a pretty effective way to generate some buzz about your new product. The first Macworld was incredibly well attended. I worked the booth for my employer -- I was scheduled for two hours on, and one hour off alternating through the day, but the reality was that I worked seven and a half hours for three days straight. My feet hurt just thinking about it. (And this was back when we wore suits and wingtips at trade shows, too)
Today, one can generate quite a bit of buzz about a new product or service just by making a press release and a couple of Twitter tweets. The internet has us so interconnected that it's just not hard to communicate.
Of course, the other thing about trade shows is that they had gotten so big that your message was getting diluted. Consider what might have happened if Apple had introduced the iPhone and CES instead of Macworld.
Chuq Von Rospach noted that Macworld caused all kinds of problems for Apple -- from people working through the holidays to messing with the delivery schedule for products. The real truth is that Apple has outgrown Macworld. Apple can generate buzz any time, just by calling a press event -- or perhaps by not calling one. That always gets the rumour mills hopping.
Apple will still have their annual WWDC as a platform for regular announcements. It's curious to me that Microsoft hasn't copied this idea. Sure, they have PDC -- but they only call for a conference when they feel there's some release of note. If they were smart, they do it every year.