Has an optional "browser upgrade" message ever worked?

From time to time, we feel the urge to encourage users to upgrade their browser, especially IE. And from time to time, we've rolled out features that attempt to send this message to users, usually "lightbox" dialogs, but sometimes as banners, begging the user to upgrade.

But nothing works. If the dialog has a "close" button, users immediately click it. If it has a "cancel" link, however small and unobtrusive, users find it and use it, even if the link says "continue at your own risk." And if it's a banner, they just ignore it, not even bothering to click a button to close the banner.

(Obviously, we could just block certain old browser versions completely, but that's an extreme choice that we wouldn't want to do to more than a few percent of our visitors.)

It's easy to brainstorm more/different ways to send this message (and there are a number of cute open-source projects to display an "upgrade browser" warning), but I'm wondering: has anyone ever rolled out a "browser upgrade" dialog that actually worked?

By that I mean, does there exist any documented case on any website where the data showed that rolling out a "please upgrade" message was followed by a sharp measurable drop in old-browser traffic?

Or even a reasonably large percentage of users actually click on a "Download" link in the dialog/banner to upgrade their browser?

EDIT: Folks around here can get prickly about proving causation, so I want to clarify: I'm not asking for data that "proves" that a banner caused users to upgrade. All I'm asking for is a documented example where somebody installed a "please upgrade" banner and observed that their old IE usage decreased shortly afterwards.

(Proving causation is hard, but if no one has ever even observed a correlation, that's a surprising and important discovery.)