_hm: That's a good question. Most businesses, of course, will welcome the publicity and ease with which people can find them, but for those trying to keep a low profile I'm not so sure. It may take a judge to decide the privacy question.
It might make sense to start with a few captive applications, such as on-campus building navigation. It could come in the form of an app that new students could download and use. The app could work in concert with the student's class schedul and help them get to the right building and then to the right classroom.
Hospital visitation might be a good one too. It could get visitors to the right room while keeping them away from areas that need to be off limits.
Being captive to an institution, the app coul alread have knowledge of all of the institutions's wireless spots and could use those for positioning inside, or out.