my photo stream only very sporadically syncs pics taken on my iPhone 4s to the iPhoto on my MBP.

on my MBP, i've got (in addition to the regular photo stream sidebar folder) an event called "october 2011 photo stream". iPhoto created it; i didn't. it's got 11 pics in it.

my regular photo stream folder (on my computer) has 35 pics.

my iPhone camera roll has 150 pics and vids. mostly pics.

the "photo stream" album on my iPhone has 16 pics.

my iCloud account is running and everything is enabled -- on my computer and on my iPhone, including photo stream.

what am i missing? thanks.