What this is, is a microformat-style, HTML-based declarative front-end onto Google Maps. Check out this sample code for placing labelled markers;
<div class="GMapEZ GSmallMapControl GSmallMapTypeControl" style="width: 300px; height: 300px;"> <a href="http://maps.google.com/maps?ll=41.092104,-85.144740&spn=0.006130,0.009795&t=k&hl=en"> A </a> <a href="http://maps.google.com/maps?ll=40.755580,-73.937988&spn=6.276505,5.552490&hl=en"> B </a> <a href="http://maps.google.com/maps?ll=41.877741,-87.637939&spn=6.169597,5.552490&hl=en"> C </a> <a href="http://maps.google.com/maps?ll=33.916013,-118.179932&spn=6.874500,5.552490&hl=en"> D </a> </div>
So the labels become the content of the anchor element. Neat. A better microformat design might have been to use “ol” (ordered list) with some styling (“list-style-type: upper-alpha”) to get the incrementing-letter result (at least for that simple case). And I’m not sure the G* “controls” really fit best in “class” (though nothing better comes to mind – hmm, what’s good for annotation-like semantics?). But this is definitely in the spirit of microformats (even if the word isn’t mentioned), and very well done.
This approach is going to be huge.