I got to say that using peoples free SMS sounds like a very good idea when it comes to making money. But on the other hand... I very much hate to get promotional SMS:es, even more than email spam. Do you screen the companies in some way to avoid the most annoying messages? How about delivering malware links with your service? And how much control will the user have? Can they opt out of for example gambling sites if they don't like these services very much?