A sizable literature has grown up in recent years focusing on two-sided markets in which economies of scale combined with complementarities between a platform and its associated `software' or `services' can generate indirect network effects (that is positive feedback between the number of...

Internet search (or perhaps more accurately `web-search') has grown exponentially over the last decade at an even more rapid rate than the Internet itself. Starting from nothing in the 1990s, today search is a multi-billion dollar business. Search engine providers such as Google and Yahoo! have...