Excellent idea. I completely agree: that would get high opt-in rates and be perceived by most people as a very fair exchange for providing the information.

Personally, I still wouldn't register, even with that incentive, so the opt-out would still be needed but this is still a very good idea.

In fact, if Nokia will open source cherry, and the SMS libraries it depends on, I would be very happy to contribute to a community project to provide this feature. I already mentioned, in my bugzilla request to open source cherry, that the community might be able to help Nokia make the process acceptable and legal while still providing them with high opt-in rates.