#8 - Sept. 10, 2010, 6:38 p.m.
Bulreporting's statement is very close to what I would have written myself. Each case is investigated individually - there's not exactly a 'clear cut' line I could give you on this situation.
Please be aware, however, that maliciously taking the items from a guild bank can fall under and be subject to our Scam Policy.
Scam Policy
http://us.blizzard.com/support/article/20459
If there is something from the Guild Bank you want, you really should discuss it with the officers or guild leader - perhaps you can come to an arrangement that is fair to both you and the guild. =)