If you work for IBM, you can bring your iPhone to work, but forget about using the phone's voice-activated digital assistant. Siri isn't welcome on Big Blue's networks.

The reason? Siri ships everything you say to her to a big data center in Maiden, North Carolina. And the story of what really happens to all of your Siri-launched searches, e-mail messages and inappropriate jokes is a bit of a black box.

IBM CIO Jeanette Horan told MIT's Technology Review this week that her company has banned Siri outright because, according to the magazine, "The company worries that the spoken queries might be stored somewhere."

It turns out that Horan is right to worry. In fact, Apple's iPhone Software License Agreement spells this out: "When you use Siri or Dictation, the things you say will be recorded and sent to Apple in order to convert what you say into text," Apple says. Siri collects a bunch of other information – names of people from your address book and other unspecified user data, all to help Siri do a better job.

How long does Apple store all of this stuff, and who gets a look at it? Well, the company doesn't actually say. Again, from the user agreement: "By using Siri or Dictation, you agree and consent to Apple’s and its subsidiaries’ and agents’ transmission, collection, maintenance, processing, and use of this information, including your voice input and User Data, to provide and improve Siri, Dictation, and other Apple products and services."

Because some of the data that Siri collects can be very personal, the American Civil Liberties Union put out a warning about Siri just a couple of months ago.

Privacy was always a big concern for Siri's developers, says Edward Wrenbeck, the lead developer of the original Siri iPhone app, which was eventually acquired by Apple. And for corporate users, there are even more potential pitfalls. "Just having it known that you're at a certain customer's location might be in violation of a non-disclosure agreement," he says.

But he agrees that many of the issues raised by Apple's Siri data handling are similar to those that other internet companies face. "I really don't think it's something to worry about," he says. "People are already doing things on these mobile devices. Maybe Siri makes their life a little bit easier, but it's not exactly opening up a new avenue that wasn't there before."

But other companies have been pressured by privacy groups over the way they store customer data. Google, for example, has come under fire in the past for the way it handles a massive database of user search data. But IBM doesn't ban Google. An IBM spokesman declined to comment further on the Technology Review story, saying "we prefer to let the story stand on its own," but there are a couple of important differences between Siri and Google that may have IBM worried: For one, Siri can be used to write e-mails or text messages. So, in theory, Apple could be storing confidential IBM messages. Apple couldn't immediately be reached for comment Tuesday.

Another difference: After being dogged by privacy advocates, Google now anonymizes search results – making them difficult, if not impossible, to trace back to an individual user – after nine months.

Maybe if Apple agreed to do something like that, Siri would be welcome over in Armonk, New York.

This story has been updated to include a statement from IBM.