Thanks for that tip. I was wondering about this too. I've been using the excellent shareware app eMaps since it was quick and was easy to copy coordinates out from any dropped pin. I just learned today why my eMaps had stopped working this past week. According to the developer, "Google has turned down Maps API services used by eMaps to display contents." :-(
I had expected that the Mavericks Maps app would at least do this and was suprised when it couldn't. It's of little use to me without it. Léonie's clever workaround is far too complicated to do many times a day.
I'd given up on Google Earth which is slow and buggy when all I want to do is quickly launch a map to find a coordinate (and then I had to copy the latitude and longitude separately). Léonie's control-click "What is here?" in maps.google.com looks like that best way for now. Thanks for that.
Before returning to Google, I'm sending a feature request to Apple.