I am also looking for an example of usage for this method. I am running into issues where my InDesign (CS5.5) script crashes or runs out of memory while exporting hundreds of PDFs, so this seems like this might be a possible solution, however there is no examples of it actually being used anywhere. All I can find is this:
void dumpFromMemoryMark (from: number)
Dumps memory allocations from the specified mark.
Parameter Type Description from number The mark from which to dump memory.
This is a very extensive guide, and it talks a lot about improving performance for a plug-in, but does not give many examples. Furthermore, this specific method for InDesign scripting is not mentioned once in the guide.