If you were subscribing to the online edition of, say, Wired, Vanity Fair or the New Yorker on the iTunes store, and you were faced with the pop-up window at right, would you opt-in and click “Allow”?

Most major magazine publishers, when shown this screen by Apple (AAPL) representatives, blanched. Each of them knew full well the kind of gravy they can make out of subscribers’ names, email addresses and zip codes under “their” (as opposed to Apple’s) privacy policies.

See, for example, the $18 million settlement Publishers Clearing House paid 23 states in 2000 for various alleged misdeeds, including misleading sweepstakes claims, fake personalized checks and envelopes tricked out to look like special deliveries.

But to everybody’s surprise — including our own — about 50% of users who subscribe to magazines on iTunes select the “Allow” button. This according to a piece published Wednesday by Forbes‘ Jeff Bercovici, who says the figure was confirmed by Eddy Cue, Apple’s vice president of Internet services.

“It turns out,” Bercovici writes, “that the publishers’ fear that Apple’s policies would deny them the consumer data they need to do business was unfounded. As often as not, to get the customer’s email’s name and email address, all you have to do is ask.”

According to Forbes, this discovery is “the surprising reason publishers are finally saying yes to Apple.”

Well, not quite “yes.” There’s still the sticky business of the 30% cut Apple wants to take — in perpetuity — of every subscription ordered through iTunes.

That so-called Apple tax may help explain why some publishers, Time Inc. included, are steering clear of iTunes subscriptions. If you want to get Time, Sports Illustrated or Fortune (which publishes this blog) delivered to your iPad, you have to subscribe through Time Inc.’s (TWX) website, not Apple’s. Once you’ve signed up to get the printed magazine, the iPad version is free.