Uptime?

[Mark]

I realise this may be the wrong list to post to, but it *is*
a question and it *is* about FreeBSD... :)

http://uptime.netcraft.com/up/today/top.avg.html

So, we know BSD is capable of stupidly high uptime, but what
I'd like to know is how? I mean, we all have to patch things
now and again, recompile kernels etc. Does this mean these
sites are running thousand-day-old unpatched kernels, or is
there some black magic going on that I don't know about?

I await your theories... :)