“Notebook computer sales surpassed sales of desktop computers for the first time in May thanks to an increasing desire for mobility, according to a survey by market research firm NPD Group.”

An article on the Wall Street journal website cites market research which puts the current market for laptops at 54% of the total $500M annual retail computer market, up from 25% of the market in 2000.
“‘Key to the increased sales … are a desire for computing products that offer portability, appealing form factors and attractive design,’ said Mr. Baker, noting that aggressive pricing from the likes of Dell Computer Corp., Gateway Inc. and Hewlett-Packard Co. also played a role.”