I'd be curious to know if there's any empirical evidence for this -- that's precisely the sort of plausible claim that might easily not be supported by the evidence.
I'm sure there's empirical evidence somewhere that can either confirm or deny this hypothesis, exactly as stated. But it's so valuable that Google isn't likely to give you a peek at it for free.
Maybe some other market research firm will sell you related information. Or you could buy a few Google ads and see, I guess. Watch out for sample bias.
Its probably locked-down enterprise computers. The old company I worked at delayed the deployment of IE7 for an entire year because of one annoying application: Documentum E-Room.
