It is pretty interesting to follow the discussion around "big days" and possible attacks following those days. There was significant chatter before the Y2k change but no major attacks happened. SANS started to discuss those big days (http://isc.sans.org/diary.php?storyid=1379) but they do not seem to see 6/6/6 relevant.
On full-disclosure lists however, there seems to be growing fear. They expect attacks on 6/6/6.
Let's see, we will know soon