At WWDC 2010, When Steve Jobs was showing some demo of newly launched iPhone 4, some glitches happened because of Wi-Fi as well as AT&T 3G reception. Steve pointed that there are hundreds of Wi-Fi stations operating from the same hall at the same time. He requested all the bloggers in that room to turn off their Wi-Fi (called them My-Fi) for proper execution of demo.
In this video, you can see Steve Jobs struggling to get proper connection for iPhone 4 demo.
Anyway, iPhone 4 is already launched with lot many new features and pre-order will start on 1’th June. iPhone 4 will start shipping to 5 countries on 24’th June and then 18 countries in July and 88 countries in September 2010.