Yeah, Apple's (NASDAQ:AAPL) iPhone is popular. But did anyone know it was this popular?

According to a new survey sponsored by Good Technology, a maker of secure messaging software for handhelds, 79% of 300 IT directors surveyed (200 in the U.S., 100 in the U.K.) say their employees would prefer to use their own devices to access corporate networks than company-issued devices. Their overwhelming choice -- 82% of those surveyed -- was the iPhone.

No one else was close, but Microsoft's (NASDAQ:MSFT) Windows Mobile was a somewhat surprising second, with 57% of IT directors saying that users were asking for further Windows Mobile support.

Nokia's (NYSE:NOK) Symbian phones were requested 17% of the time, as were handsets based on Google's (NASDAQ:GOOG) Android OS. Palm's (NASDAQ:PALM) Pre ranked just above "none" with 14% of respondents.

Research In Motion (NASDAQ:RIMM) was noticeably absent from the survey, but that could be for a good reason: The BlackBerry is already widely issued inside companies. CIOs and IT managers are used to supporting the device.

That could be worrisome for RIM. If the theme of the survey is that users prefer their own devices to the corporate standard, do the results mean the BlackBerry's being replaced? I wouldn't go that far; RIM's recent earnings results still show far too much growth.

But the iPhone is growing mightily, too. Apple CEO Steve Jobs told those gathered for last week's iPod announcements that the company had sold more than 30 million iPhones to date. Many of them, apparently, are making their way into enterprises, and IT managers are making do -- even with 28% of respondents reporting security breaches because of unauthorized device use within the enterprise.

That leaves CIOs and IT managers with two choices: Either ban unauthorized use, or figure out how to better secure the iPhone. Expect them to choose the latter.

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Fool contributor Tim Beyers had stock and options positions in Apple and Google and a stock position in Nokia at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. The Fool's disclosure policy is out of things to say. Tune in next time.