No.
You can clear the logs, but it's said in the instruction booklet that it only hides the icons, not the activity.
the activity log comes back when you play it again.
It's used to make space visually in the log book if you played too much games.
(I don't know about the Format function in the settings).
It does clear the whole log when you format, but you won't have your old save data. ;_;
QUOTE(kbf @ Jul 28 2011, 02:44 PM) "when you play it again" I don't completely understand. can't I just wipe it and then not use my flashcard on my 3DS ever again so they won't see it?