Ask a European mobile-phone exec about fourth-generation cellular technology 4G and you can almost see them bite their tongue. These are the same folks, remember, who just five years ago couldn't stop talking up third-generation technology. The pitch went something like this: 3G services, with their high-speed wireless Internet access, would allow us to use our mobile-phone handsets to do everything from making home videos to surfing the Web. If investors would just give them billions of dollars, telecom operators would have the whole world plugged into 3G by, oh, about 2001.