Apple’s success with consumers has begun to spill over into the enterprise market, with Mac adoption among enterprise customers increasing four-fold in less than two years.

Mac use in businesses rose from 1.1 percent in October 2006 to 4.5 percent in June of this year, according to a report by analyst Benjamin Gray of Forrester Research released Friday and made public by eWeek’s Joe Wilcox.

While 4.5 percent of the enterprise market may appear puny next to the nearly 95 percent held by Microsoft’s Windows, it is nevertheless startling that the Mac has made any headway at all in a market in which it had languished for years.

An array of stubborn perceptions made the Mac a pariah platform in the enterprise. Windows PCs were cheaper. IT departments didn’t want to support a second platform or deal with Mac-Windows network integration issues. Many disliked the Mac because only one vendor manufactured it, meaning no competitive bids and no replacement vendor if Apple went under.

Meanwhile, Apple rarely bothered to court the enterprise, preferring to emphasize its identity as a consumer technology company. Given Apple’s exploding growth in recent years, it’s hard to argue with the strategy.

Somewhere along the way the efforts to win over consumers, particularly its emphasis on ease of use, began to sway opinions in the enterprise.

“Apple’s singular focus on user experience has resulted in some success in the enterprise – without even trying to break into the market,” Grey wrote in his report.

The Forrester report also cites virtualization (the ability to run a different operating system in addition to the one native to the computer) as a reason businesses have taken more interest in the Mac, but today’s Macs go beyond virtualization.

Thanks to their Intel-made CPUs, current Macs can run Windows XP or Vista not only in a virtual environment, but also natively via Apple’s free Bootcamp utility. That versatility removes much of the risk IT heads associated with buying Macs.

Wilcox predicted the iPhone’s popularity would create a “halo effect” akin to that the iPod had in attracting more consumers to the Mac. Apple in fact has made a play for business customers with the iPhone by adding support for Microsoft Exchange, which most businesses use to run their e-mail.

Many executives once loyal to Research in Motion’s BlackBerry now own iPhones and have started pushing their IT people to support it in-house. Since the iPhone runs Mac OS X, support for Macs isn’t much of a leap.

Finally, Gray offers this reason for Mac growth among businesses: “Tech populism drives younger, more tech-savvy workers to buy whatever they need to work smarter, faster, and cheaper.”

Today’s students are tomorrow’s young workers, and ever-higher numbers of them are Apple customers. In a report released earlier this month research firm IDC said Apple had regained the lead in notebook sales from Dell with 36.5 percent of the market. Dell sunk to 27.1 percent.

“What we’ve seen over the past couple of years is a significant increase in the number of students who own an Apple laptop or Apple desktop or plan to buy one,” Eric Weil of Student Monitor, a research company focused on college students, told Investor’s Business Daily.

It all adds up to another perfect storm for Apple, and another reason why it could enjoy year-over year Mac sales growth of 30 to 40 percent for quite a few quarters to come.

Imagine what would happen if Apple actually put some effort into selling Macs to the enterprise. Yep.