According to the news, they have decided to expand their Linux support to selected desktop and notebook systems. On their official blog, they have posted more information about this. Dell will first certify that the hardware that they sell is supplied with all the necessary drivers to run Linux. That's the primary concern of the users, and not which distribution to support.
All is well in this world then. I'm quite surprised that more than 100,000 people actually took part in the survey. I personally didn't. With a sample size like that, I'm fairly certain that there aren't that many Linux fanboys out there to skew this survey. It's quite possible that a lot of the people who took the survey were IT consultants and managers. The kind of people on the line who will affect purchasing decisions and are sufficiently knowledgeable to know a good decision when they see one.
Competition is good. By having a OS choice, Dell may benefit from the leverage it can put on Microsoft. In the past, when there wasn't much demand for Linux, Microsoft could dictate terms. Now, if Dell can show that they can post a profit by selling Linux based machines, and prove to the other Tier 1 vendors that there is *actually* a market for Linux based PCs, Microsoft will suddenly have to play the courter, rather than dictator.
Dell has already shown that it is capable of breaking 'special relationships' when it started shipping AMD based machines side-by-side with Intel ones. It probably lost a significant amount of co-marketing funds from Intel for that. However, it must've made more customers, since they have expanded their AMD based product line from the initial servers, to desktops and notebooks now.
So, I'm fairly certain that Dell has considered the amount of co-marketing funds it's going to lose from Microsoft if it starts shipping Linux based machines side-by-side. However, it has to remember that it's selling boxes, not software. If Linux will help it ship more boxes, then, that's the way to go. Dell must've done their market research and concluded that they will make more money doing this, than by ignoring their customer requests. Now, if only Dell can do something about the design of it's boxes....