Set passcode to appear "immediately" -- if you set it for 1 min/5 min/15 min/1 hour/4 hours, then this "vulnerability" really isn't one.
As a side note, one can use this bug to access contacts list and send email on behalf of the owner (via share menu in photo stream).
Edit:
Just found out that I can tweet, post to facebook and send email just by using Siri (if that setting is enabled). Although, this might be the correct behavior.