2. The existing loopt software is j2me, which the iphone conspicuously doesn't support.
3. Loopt does have a website, not sure how well it works on n iphone, but since the iphone is basically acting like a small computer (no gps, has a mouse) it seems like the proper channel to the service.
I can't think of many problems that require GPS.
It's extremely valuable in all sorts of applications. Google maps + GPS would be amazingly useful and would severely damage Garmin's market. I would use it for mapping my bike paths and "geomarking" great restaurants.
I doubt others will get a chance to implement it because it would require low level access to the wireless hardware, but I really am not qualified to comment here.
I think apple probably wanted GPS but had to axe it for battery life and/or form factor (both spec's probably sitting at hard requirements from the early stages of the phone's design). So then I'd expect GPS to be on future models.