It's an all too common response to the question of using .NET code.
I can't guarantee clients will have .NET installed (actually I can pretty much guarantee they won't)
Exactly why the .NET Redistributable and it's prerequisites couldn't have been released in a service pack for the various MS platforms is beyond me. How successful will ClickOnce be if code can't run on most clients? No-touch deployment has to-date largely failed NOT JUST because you have to touch it first (change the security policy to do anything of consequence), but also because most clients don't have .NET installed anyway.
Update: dare we hope that it might be included in XP Reloaded?
Update: September 2004 - 6 months later - no luck.Microsoft just don't seem to even see it as a real problem - check out this post by Brad Abrams of Microsoft