Hi, I have a map which plots ~400 markers from an XML file (code taken
from the example files). Firefox warns hat the script is running slowly
- it does. Any suggestions how to speed thinks up, or the maximum safe
number of markers if I have to split the map up?
Thanks.

I have the same issue, and I've found that 25 is a good number.  It's
highly dependent upon the client's computer, so even if you have a nice
fast system it may trudge along on another system.

I have a lat/lon dataset from 3300 users of my community site that I'd
like to plot on a US map, so of course I get the same warning in
Firefox when I try and load them all up as an array. Is this beyond the
bounds of what I can expect from the maps API? Should I just limit the
data to state by state (some states still have hundreds of records).

Do you really need to show all users at the time? If not, use AJAX to
continuesly fetch the data of the markers inside the shown area of the
map.

It's not a limitation of the Google Maps API, it's a limitation of
browser resources.  It's just an expensive operation to load up markers
and have an application surrounding them.  JavaScript isn't a language
known for it's massive performance benefits.

I'd recommend using some method of pagination or heirarchical grouping
of data until you can reduce your result set (look at events to handle
scrolling and zoom level)

I'd say 100 is the maximum you should hope for, 25-50 is the sweet
spot. It really is just the XML processing that's going on. I've found
that FireFox is a lot better than IE too, which takes about 4 times
longer and hangs the system while plotting them.

Do they have to be displayed on a web page. If you generate a KML file
(KeyHole Mark Up) then you can show them on Google Earth, I pretty sure
that can handle pulling in 3000+ records.

This is a very intresting idea... could you point us to some code to
help with that?

I assume it would at least involve:
        var bounds = map.getBoundsLatLng();
        var width = bounds.maxX - bounds.minX;
        var height = bounds.maxY - bounds.minY;

Then use that data to do a query for items within that range.

David S. http://www.seemsartless.com/map/

Just as another data point, I successfully plotted 500 points.  It took
right at 3 minutes in IE, on my P4 3.0Ghz 1G RAM desktop running XP.
IE threw up a warning after the first minute.

The points were hard-coded javascript, i.e. not being read from an XML
file.

For what it's worth, the map moves around and zooms at "normal" speed
once the markers are all plotted.  Also for what it's worth, the
initial zoom level makes no difference regarding how long it takes to
load the points.