I’ve noticed on a client map that hovering over unclickable markers (with titles) no longer shows a tooltip.
It seems as if Google changed this!
Here is a 2009 GMapsV3 tutorial showing a tooltip for an unclickable marker. The tooltip doesn’t show (anymore)!
I think the “clickable: false” option makes the difference. With clickable disabled you don’t get a cursor-pointer and no title. The tutorial from 2009 loads always the latest version of the api. Google does change a lot of things in every minor version.
Here is the changelog but i does not find an exact match where this change was documented:
http://code.google.com/p/gmaps-api-issues/wiki/JavascriptMapsAPIv3Changelog