Sounds like you might be interested in marker clustering. It's easy to enable for your map in the xml. Just set the "markerClustering" attribute to have a value of "enabled".
<map latitudeAttribute="latitude" longituteAttribute="longitude" markerClustering="enabled">
.
.
</map>
The clustering is done by grouping markers located in fixed grids on the map and is implemented using a default Google Map API clusterer.
It is actually described in the official documentation too:
https://wiki.mezzanineware.com/x/C4QOAQ