Regarding making money - I'm not sure yet. There would be a few options - including either charging members per lunch or charging restaurants. However, I'm planning to wait and see how the service evolves before I start thinking about that too much.

The problem of signing up for lunch and not having anyone to match with is definitely something I'm trying to avoid. A couple ideas (not implemented yet) - warn people that there are very few people signed up in their area. Allow matches with 3 or 4 people (so there is not an odd man out type situation)