KML files can be shown on Google Maps once they've been uploaded to a site. Some limitations/bugs in Google Maps required modifications of BT747 available starting from V1.60.12.
Some samples follow below:
474kB - Track + Track Points with Name only
75kB - Track Only (no Name, no Info)
790kB - Track + Track Points with Info
837kB - Track + Track Points with name and Info
The options above correspond to the 'Add Track Point Info' and 'Add Track Point Name' options on the 'Output Settings' Panel. As you can see, when track point information is not written the file is about 10 times smaller than its biggest version.
Obviously, the best choice for this kind of usage is to disable the Track Point Name and the Track Point Info. Not only will the resulting file be smaller, Google Maps will also work better. At the time of writing it does not always show the track correctly when the other options are enabled.
You can compare this with the direct Google Maps HTML output by BT747, which is only 12kB 'small' and yet has all the track data that you see on the map (i.e., equivalent to the 75kB file above) !