I use the same disk to install LM on at least 4 systems. Often my laptop, a dual boot on my other laptop at work, my dads laptop, my housemates laptop, my colleagues desktop and sometimes dads mate's laptop. I know that's 6 but sometimes it varies. I've also installed it on student machines as we often pass the disk around (they have their laptops in college) so this would be 10+ (I encourage they download their own as a backup and also to help with the download stats).
How many different installs do you perform from one download?
Maybe this will help to guage usage better? I thought this may have been done already but I searched for it and I couldn't find a similar poll. No doubt someone will point one out that was there all along that I didn't see
If your installation amount varies with each release then just take an average.
(I'm looking at LM17 here but any realease still qualifies).