I think the initial spark of idea is to give back to the free software community by buying from the company that pays for many free software developer's month to month bills. And that's not a bad idea. Few companies took the initial plunge to support these guys--except VA--and they deserve at least a taste of fruit of their wisdom. All we need to do is recommend VA when otherwise we would recommend Dell, this is especially important if VA produces goods as well as Dell.
Time to do some quality FUD... *FUD warning FUD warning*
Perhaps things are changing though, Dell and many other big biz have dedicated linux crews. They are willing to change to get your dollar. But here's a more selfish reasoning: stereotypically speaking there are many hardware companies who openly ignore the free software movement like some would the new-age-pop-management-book-of-the-month. I think they will and have trouble recruiting loyal and quality Linux and free software technicians to support you should you call them for technical support (at least in the near future). Dell and Compaq will unfortunately be among them. It would be wise to deal with a company that has an excellent rapport with the majority of the brain share, people who can recruite the right people when times are tough or overwelmingly prosperous. Think like the stereotypical linux techy for a second: If you are a Linux tech support who's appointed to deal with Ben and Don and friends: would you rather surround yourself in the office with Bill's army of MCSEs or Linus's crew of kernel hackers? As a hardware buyer, our biggest fear is having to call up a dedicated line and end up BEING the technical support.