Re: map.centerAndZoom() has to be before adding any markers?

Yup. I noticed the same thing (I got an error on "this.topLeftTile"
when an initial map.centerAndZoom not done)
http://groups.google.com/group/Google-Maps-API/browse_frm/thread/c6dab11257a84640/90f00b785137cafb

There is no problem picking an arbitrary point then re-centering the
map.

-- Larry