When Apple opened its iTunes App Store in July, the idea of a mass-market Web site that sells downloadable games, tools, and other applications for cell phones was a rarity. Handset owners could buy apps from their carriers or the occasional niche site. But these days, the app store concept is becoming commonplace. The question is, does the world need a warren of wireless app stores? In the coming six months, at least four would-be rivals of Apple will probably open their own online bazaars where developers of all stripes will sell downloadable software applications.
