I have a cell phone, you don't have the number, and I want to keep it that way. But if some of the good people in the cellular phone industry have their way, I soon might have to pay for the privilege of privacy in this case, just like I have to in other dealings with the phone world.New reports surfaced at the end of May that the Cellular Telecommunications & Internet Association (CTIA) was developing a directory that would include listings for about 75% of the 164,424,519 million U.S. cell phones. (The number comes from www.ctia.org and was current on May 31 at 3 p.m. EDT.)Steve Largent, president of the CTIA, was quoted as having said: "This system will provide consumers an opportunity to opt in, if they choose." Pardon me for scoffing.The chance of the CTIA getting more than 120 million people to individually authorize it to include their cell phone number in the directory is small. Largent is being disingenuous at best. Almost all the authorizations that he seems to be referring to are buried in the fine print deep inside the contracts we have to sign (and are not permitted to modify) when we get cell phone services. Hardly the individual "opt in" that Largent implies.The phone companies have dealt with this sort of thing before. They have a simple answer: Make the customer pay. It costs me $1.21 per month to not have the number of my fax machine listed in the printed Verizon white pages directory. It would cost an additional fee not to have the number handed out to people who call directory information.Because the CTIA is not likely creating this directory out of the goodness of its heart, the group must have a business model in mind. Because this is a major project, one would think there would be information about it on the CTIA Web site. But the only mention I can find is in an article titled "Wireless directory brings up privacy issues" on the "daily news" page for May 20. This article mentions that Rep. Joseph Pitts (R.-Pa.) introduced a bill to block the inclusion of cell numbers in directories for people who have not actually authorized it and mentions that Verizon said it would not adhere to such a rule, which means I do not have to worry about the threat for myself - yet.One business model would be to extort money from people who did not want to be included. Press reports say that the CTIA says this will not happen, but I haven't found where the group directly says that. I wonder what the business model is. How the phone industry deals with this directory may foretell what will happen with\u00a0Enum. Enum is an IETF technology that will be used to map phone numbers into Internet URLs. There are a lot of potential uses for\u00a0Enum.This situation with the CTIA is another case where customer opt-in will be vital for preserving privacy. It would be nice if the "opt in" actually meant it. We'll see if CTIA can understand the concept.Disclaimer: Developing and understating concepts is the raison d'etre for a place like Harvard, but this observation is my own.