I used to, yes. I still do, sometimes.
Except those that I converted to Linux and who learned better methods (security-wise, I mean). Those, I check upon every few months, and they simply tell me "everything's fine, no problem, it works perfectly". Sometimes, they add "it's very simple, in fact, and I don't have to bother you with questions because, well, the answer is usually online", or "it's very fun! I found out how to do this, this and that! Did you know about it?"
I scratch that: one needed some more help one day when attempting to "sudo apt-get dist-upgrade" from Ubuntu 7.10 (which was itself an upgrade from 7.04) to 8.04 (a known UTF-8 conflict in that particular setup that took a dozen minutes to solve).