Supporting Multiple-Location Users. Jakob Nielsen's Alertbox, May 26, 2002. About half of the users now access the Internet from more than one location. Despite the implications of this for service design, many systems assume that users remain bound to a single computer. [ia/ – news for information architects]
Another interesting quote from the article:
I know people who synchronize their office and home PCs by keeping both synchronized to a brick they strap to their belt and carry back and forth. The brick may be called a Palm Pilot, but it's still as close to the Stone Age as you come with modern technology.
The article's key assumption is that the locations from which one accesses the Internet have high-bandwidth connections. That may or may not be true. One has to design a product taking the uncertainty of bandwidth into account.