The fact that you have such a large number of laptops in your possession suggests to me that you're probably in a corporate IT setting (apologies if I'm wrong). In such a case, Hardware failures are probably going to be the most prevalent mode of failure for needing a system re-image, since software usage is going to be in-line with corporate policies. People aren't going to venture into warez sites, etc.
But for the average, non-technical user, I think you'd see a much higher incidence of needing a system re-image due to viruses, malware, spyware, etc.
But then the average user is likely to take it to any number of computer repair shops who might try the recovery partition, or they might just reimage from an OEM install disk they have lying around/available.
The people hosing their system like that aren't likely to be able to use a recovery partition. I would guess they'd take the computer to a shop to get it fixed.
But for the average, non-technical user, I think you'd see a much higher incidence of needing a system re-image due to viruses, malware, spyware, etc.