At least at a high level I can!!  The code comments in ChunkPointPlaceholderEventSource actually explain it reasonably well.  Basically, you put a chunk-point around content that is user-specific.  I interpret that there must be some hash function or something to allow the portal to determine "common" content that's the same for everyone or perhaps many people so it is not stored or processed each time for each user.  I would like to dig into this in more detail but I think I understood it well enough to toss it in where I thought it made sense.