In part, Wap was a victim of the dotcom hype machine that tended to over-inflate the value of any technology if it had even the vaguest connection to the Internet. More seriously, Wap provided a solution to the wrong problem: accessing today's Internet from mobile phones is not a particularly sensible thing to attempt.
The success of the Japanese i-Mode system does not contradict this, since there the particular local conditions have tended to outweigh the inherent disadvantages of today's screen sizes etc.
It may well be that Wap was wrong not so much because it tried to bring the Internet to mobile phones, but because it sought to shoehorn the entire Web into these devices. The problem here is twofold: graphical elements form such an important component of online browsing, that losing them robs Web pages of much of their power. Similarly, the crucial hypertext links are reduced to deeply-nested menus, which tends to nullify their ease of use.
But there is another hugely successful Internet application that avoids both of these issues, and which seems perfect for mobile phones: instant messaging. A very simple form of wireless instant messaging already exists in SMS, but some companies are now suggesting that a messaging platform as rich as the main Internet instant messaging services might turn out to be the right way of marrying mobile phones and the Internet.