Are there valid KML tags that will cause the API to refuse to display a KML file?

[Joseph Elfelt]

We know that the API will refuse to display a KML file if:
1. It exceeds 3 MB
2. It exceeds 50,000 (!) features
3. It takes over 4 seconds to load (?to start loading?)

I suspect there might be a 4th reason. I think there might be valid
KML tags that mean something in Google Earth but which will cause the
maps API to refuse to display the file.

If so, it would be useful to compile a list.

Can anyone shed light?

[Chad Killingsworth]

Did you have specific tags whose presence caused your KML layer not to render?

[Joseph Elfelt]

No I don't. Instead I have an app that can read KML/KMZ files.
Sometimes when I try to look at a file that ought to display given
the specs as we know them, the API refuses to display the file.

Hmmm....On further thought I guess the first thing I need to do when I
encounter a file that is within the size specs but does not display
with my app is to download it and then put a copy on Google Sites.
If I can display it from Google Sites (fast servers!) then the root
of the problem was a slow server where the file is originally hosted.