This work-at-home thing seems to go in cycles, depending on how a company is doing financially. This article in BusinessWeek claims that companies are offering incentives for some workers to stay home and phone it in. Great picture, by the way--very apt. I work at home, and I don't miss the daily commute, or the office politics, one bit.
Keeping the others who inhabit the same space out of the office is sometimes an issue, as this Dilbert strip accurately depicts.