The New York Times reports on developments since both Google and Yahoo published documentation in recent weeks that made it easier for programmers to write code linking data to web-based maps - and to satellite imagery, in the case of Google. This summer, Microsoft's Virtual Earth will join the fray.

All three online powerhouses expect their map-based services to become vital to the next growth area in online advertising: contextual ads tied to specific locations. Ads would be embedded in maps generated by a search query, or run alongside the maps.

"There are billions of dollars of commerce down the road," Chris Churchill, chief executive of search-engine advertising firm Fathom Online, is quoted as saying. "It will all be an advertising-supported model."

The Times writes that a likely model for the makers of programming tools would be licensing on the basis of a revenue split from the advertising generated by use of the maps. Already, there has been a burst in the creation of application programming interfaces, or APIs, for the map services.

According to the article, those new services and APIs represent a shift to "Web 2.0," a new generation of internet software and technologies that will fit together, "much like Lego blocks, in new and unexpected ways."