The biggest hurdle to biking and walking, for those who are already comfortable doing those activities, is showering. I don't want to show up to the office drenched in sweat, making the work area smell like a gym. And there are some things that you can do, like the wipes and that, but they don't feel anything like a shower. The more offices that either put in showers, or locate near gyms and places that do have showers, the better.