A 411 directory of cell phone numbers should debut by the end of the year, leading some wireless carriers and customers to air concerns about privacy. But the companies taking part in the directory promise cell phone numbers will only be included if owners opt in.

Greg Keene, chief privacy officer of Qsent (search), the Portland, Ore., firm behind the directory assistance technology, insists cell phone numbers will not be forced into the public domain.

"Privacy and security are the No. 1 concern of all the participating carriers and Qsent," Keene says.

Qsent has promised never to sell or publish the millions of highly coveted cell phone numbers it anticipates in it database. But Connecticut's attorney general calls the directory a solution in search of a problem.

Cell phone users "may be charged for calls made to their cell phone numbers, they may be promised confidentiality and then find that the list somehow mysteriously becomes available to telemarketers," Richard Blumenthal warns.

However, even if an unscrupulous carrier sold its cell phone numbers, those telemarketers are prohibited by federal law from ever dialing them.

Moreover, not every cellular company is sold on the idea of a wireless directory. Verizon (VZ), for instance, says it is concerned about its customers' privacy and, along with one other major regional carrier, will not share its customers' numbers with the directory.

"It's what you are potentially opening yourself up to ... unsolicited phone calls, unsolicited e-mails, text messages, pictures and videos," Verizon Wireless spokesman David Samberg says.

While the directory could provide a valuable service, watchdog group the Center for Democracy and Technology (search) says, falling short would be a headache for both carriers and customers.

"If this gets out of control," CDT's Jim Dempsey says, "If the marketers do in fact start using this information, people are going to turn off their cell phones, and that's the last thing the cell companies want."

Click in the box near the top of the story to watch a report by FOX News' Todd Connor.