I would support a law that would mandate a bottom-up approach to telecommuting in the Federal Government; in other words, if gov't workers want to telecommute x number of days per week, they are allowed to - no questions asked - unless their jobs require them to be in secure locations, etc. I would like to see gov't managers having to justify their employees' commutes to work, according to rigorous standards. A telecommuting program like this would also require gov't managers to associate their employees' jobs with very specific, measureable tasks that can be completed at home and turned in according to specific deadlines, like in the corporate world.
I would also want to see this program become a point of preference for contracting with the government- basically, if a company wants to do business with the federal government (the largest purchaser of goods and services in the world), they would have to have their own similar telecommuting plan.
I see the effect being a massive decrease in commuting cars on the roads, with better retention of employees in compliant organizations.
This and other sites deal with the benefits, but aside from the plunge in commercial real estate, I haven't thought of any other unintended consequences.
http://www.mite.org/FAQ/faqgenl/faqgenl.html