If you don't know Kam VedBrat, you should. To a large extent, he is the one who helping make sure that Windows Vista is going to be customizable by users in a real way. At Microsoft, Kam is responsible for a lot of the UI work on Windows Vista. And he is constantly under pressure from well-meaning users who argue that Microsoft should "build in" advanced "customization" features.
The problem that those users don't realize is that if Microsoft were to put in too many customization features it would essentially kill off third-party customization and Microsoft is never going to put in the kind of customization that third parties would dedicate themselves to as long as there's a market. Put too much in the OS and the amount of work third parties have to put in to reach the threshold in which a user would pay for it would become too high and those developers would find something else to do.
But let's explore it though for a moment. Let's put aside the branding issues (the more Microsoft supports customization as part of the OS, the weaker the Windows brand becomes) and let's put aside all the support issues that would rise as users downloaded third party "skins" that weren't compatible with this or that app and called up Microsoft. Ignoring those two issues (which in themselves are show stoppers), the problem is that the really cool customization apps we've seen over the past few years would never have come out if something even half as good were part of the OS.
The vast - VAST majority of users are happy with Windows as is. 95% of users of Windows XP are using the plain blue "Luna" UI and most of them are probably using whatever wallpaper came with the computer. Of that remaining 5% all but a small percent are content with changing to the silver or green (okay silver) Luna. That leaves about 1% of the user base who wants more. How much should the other 99% be charged so that the 1% can be made happy with customization when there's a proven market of third party developers who are able and willing to devote resources to create something far more advanced than what Microsoft could ever justify?
Whether you use a feature of the OS or not, you're paying for it. And if only 1% of the userbase would use a feature, why should the other 99% be charged for it? Sure, in absolute numbers, 1% is huge. But in terms of percentages it's trivial.
But let's say Microsoft bowed in and put in say skinning and custom shells and super-duper icon tweaking and countless other things. What would happen? The third party developers would go off and do something else. Anyone who thinks that developers would roll up their sleaves and come up with something super fancy still is kidding themselves. Anything really sophisticated takes a lot of time and that eventually means the developer needs to be compensated. If the "low hanging" fruit features are all part of the OS, then those developers will find some other niche (some other type of utility, another OS - the MacOS market is getting interesting after all <g>), etc. The net result is that you just wouldn't have the kinds of customization options. You'd end up with fewer choices rather than more.
There'd be no market left other than maybe some freeware developers tweaking on the outer edges. And would the vocal minority who demanded these features in the first place be satisfied? Probably not. Because they would then be joined by the much larger group of people who didn't see a big deal paying 10 or 20 bucks for a utility that did a bunch of really cool things that aren't being updated or made anymore. Microsoft would be stuck with the "responsibility" of supporting and placating those users. And for what? What's the business case? Would those vocal users not have bought Windows? Not have upgraded? Of course they would.
From Microsoft's perspective, going around adding tons of tweaking features or skinning features to the OS is a lose-lose proposition. They weaken their brand. Increase their support costs. Kill off the ISV market where a lot of innovation on Windows comes from. And they don't sell a single copy more than they would have anyway.
So all users who like customizing the way Windows looks and feels in interesting ways should be glad that Kam VedBrat is the Lead Program Manager for the Windows Client Platform Team.