Millions of fingers scurrying over mobile electronic devices probably paused this week as news emerged of a trove of text messages containing flirty and sexually explicit chat between Detroit Mayor Kwame Kilpatrick and a top aide. Even those engaging in more wholesome dialogue would be wise to wonder: Do text messages disappear like oral conversations or are they permanently logged somewhere for potential retrieval like e-mail usually is?

For standard consumer text-messaging technology, the answer is largely that they disappear. But Kilpatrick's and Chief of Staff Christine Beatty's devices employ less-fleeting technology.

I think people can feel comfortable we're not storing information that can later be used against them, Verizon Wireless spokeswoman Erica Sevilla said. Unless you have something stored on your phone or on a recipients' phone, it does not stay on our network for a long period.

AT&T Inc. keeps text messages for up to 72 hours until delivery is successful, spokesman Howard Riefs said. If a message can't be delivered, it is removed from the system and can't be retrieved.

Kilpatrick and Beatty testified last summer in a whistleblower trial that arose from a lawsuit filed by two police officers alleging they were fired for investigating claims Kilpatrick used his security unit to cover his extramarital affairs.

Kilpatrick and Beatty denied any sexual or romantic ties in 2002 and 2003. But the Detroit Free Press said in a story published Thursday that it examined 14,000 text messages on Beatty's city-issued pager from those years and found many examples.

The city's text messaging service is provided by Mississippi-based wireless company SkyTel.

Roger Pondel, a spokesman for SkyTel's parent company Bell Industries Inc., declined comment Friday.

SkyTel's devices employ a technology called Narrowband PCS, including two-way paging, that rose and fell in the mid-1990s, according to David Chamberlain, a wireless analyst with Scottsdale, Ariz.-based In-Stat.

Chamberlain said SkyTel's device is more akin to e-mail than to text-messaging, and messages are stored. While mainstream technology has since moved to SMS or Short Message Service technology, some corporations and governments have stayed with wireless services like SkyTel.

It was going to put mobile messaging in the hands of lots of people, Chamberlain said. (But) it was so poorly differentiated from text messaging. It required people essentially to have a second, very expensive message-only account.

SkyTel's contracts with corporations and governments say communications will be stored for legal reasons. And Chamberlain said users of any technology should know that when using any device issued by an employer.

There's absolutely no expectation of privacy with phones, e-mails, text messages or computers, he said.

While people may feel comfort knowing their text messages aren't permanently stored, that doesn't mean they should let their guards down when it comes to electronic communications, said a spokeswoman for an online privacy advocacy organization.

The whole concept of data retention by third parties ... is going to be the big privacy question over the next couple of decades, Rebecca Jeschke of the San Francisco-based Electronic Frontier Foundation.

We trust so much of our communications and thoughts, even, to these third parties who are capturing this information and storing it in various ways. It's time for us to think about it.