Researchers in LA are trying to help world's biggest media companies and their high-profile clients understanding the divided consumer's attention span (source: NYT):

The Emerging Media Lab is run by Interpublic, a holding company for media- buying firms like Universal McCann and Initiative. Since February, clients like Sony, L'Oréal and Microsoft have been using the lab to try to figure out how to reach consumers who seem to be doing so many things simultaneously. (...) Market researchers as a whole are struggling to understand the realities of what often is called "concurrent media usage." (...) For advertisers, the challenge is getting the message across in one medium while the consumer is simultaneously active in several media. (...) In the Emerging Media Lab, advertisers can observe "engagement." Using cameras that feed back into an observation room, advertisers watch consumers use old technologies or try new ones.

But it does seem that a consumer who is multitasking is not devoting an equal amount of interest to all those activities. "Terms like multitasking imply equal attention," said Mike Bloxham, director of testing and assessment at Ball State University in Muncie, Indiana. "But cognitive science tells us this isn't possible. You have to give priority to one in order to absorb the messages."

Research or market research? It's clear that they are facing a real challenge but I tend to be quite pessimistic towards the advertisement world, which is actually not so much of a problem to me...