I agree that mailing list subscriptions probably don't tell you much.
Here's a little bit of data, though:

I recently (a few weeks ago) logged back into my undergraduate
university's math department.  There I was surprised to see that they were
using NetBSD (they had been using GNU/LINUX and some SGI's when I left a
couple of years ago).

Just the math department uses about 50 NetBSD machines, I'm now told
(including "all the major servers").  So probably anyone with an account
(that would include the faculty and grad students, as well as at least
some undergrads) are using NetBSD in some form.  Even if some faculty keep
Mac's or MS-WINDOWS on their desktops (I'm sure that some do), they have
to get their email from somewhere...(^&


Many of them probably don't really know or care, of course.  I doubt that
any of the students or professors read these lists.  But, most or all of
them are NetBSD users nonetheless.

I have no idea how well NetBSD may have made inroads in other departments.
(The EECS department machines shuffled around; I'm not even sure I have an
account with them anymore.  And I never had accounts with any of the other
departments.  The EECS department *did* have an Alpha server running
FreeBSD for a time; I can only assume that they chose FreeBSD over NetBSD
for SMP, but no one ever said in my hearing.)


  ``I probably don't know what I'm talking about.'' --rauch@math.rice.edu