I see your old map app and a raise you a collaborative multi-user map app http://multimap.wakawakafoobar.info/
Multiple people can view and control the map in realtime. nodejs, socket.io, dnode, and google map api.
Agreed, this seems to overlap completely with Google Places: http://www.google.com/lbc
This looks like one of the hundreds of startups launched in 2004 with the idea of "Put pins on a Google Map and save it in a database". Lots of those startups got funding for it, and they've all run their course.
Since the functionality you're planning to build is now actually built into Google Maps itself, what's your purpose with this thing?
From an implementation standpoint, I'd ditch the "name your map" and "log into google" steps. Start off with a randomly generated unique URL and let the user immediately start sticking pins into a map. If they decide to "save" at some point, you can hit them up for account details. That's the standard way of doing things like this these days.