Netbooks are identical to laptops in this sense: their manufacturers consider failure information to be proprietary, and won't release it. So actual, industry-wide, figures are effectively unobtainable.
In a general sense, however, you're more likely to have a hard drive or a fan fail than to have a solid-state component like RAM fail. Netbooks, like laptops, are subject to a wide variety of vibration damage due to their mobile nature. Screens will be cracked, machines will be dropped.
If you're thinking of deploying netbooks en masse I'd suggest getting the maximum warranty on each one and sending them back whenever they have an error, and making it the manufacturers problem. When the warranty expires, throw the dead ones away. Where I work, we've been doing that with laptops for years, and it's really streamlined the whole process...Maintaining mobile computers is such a huge p.i.t.a, that it's far more economical just to have a few dozen spares lying around, than to have a bunch of guys whose sole job is to try and fix broken ones.