Incorporating a user editable map into a website

Exactly what part of the map would you want edited? The actual imagery / roads etc or pointers on it?

Yeah, I'm sure something like that is possible. It's definitely easy to put placemarkers on a map using whatever technology you want (e.g. a site like daft.ie putting placemarkers on a map to show houses).

I don't know what the Google Maps API provides in terms of any user dropping a marker on a map on your site, and you being able to capture and save the details though.

Try their documentation and see what it says.