Notifications should be limited to the messages visible within your bounding box. If I've zoomed in on a city, I don't want notifications from somewhere half-way around the world.
Yes! Right now it is just broken :) you get an endless stream of notifications, I will add a very simple distance filter.
I'm not so sure about distance. Maybe based on your zoom level? Because if you're zoomed out, I'd guess you want more notifications than if you're zoomed in on a city or region.