I know first hand from a District Overseer that they are NOT grounds for Disfellowshipping. This, of course, came as a COMPLETE shock and surprise to the other rank and file Witnesses that were involved in the...uh...discussion...
I was also going to post up that Awake! article but someone else did. While that article is about as clear as normal, it does open the crack of the door for interpretation just like being allowed to vote a few years back.
This is a fight near and dear to me and I have fought the good fight on this one many times. Birthdays are A-OK! lol