What's being imagined here is a mashup of google maps with multiple data sources, some of them static, some of them dynamic. For those resources where the data source is generic it is probably best to provide that data in a form that can be cached: locally, at the mashing up server, and in a web conscious way. For example the waypoint data for NOAA Towers might be useful as a service that takes a current location and returns a JSON list of waypoints that are within some radius of that location (note that google maps has a similar feature which basically says is this point within this boundary, but presumes that we already have data). If that service is unreachable, however, we're kind of SOL, so...