#3 - Sept. 9, 2010, 12:07 a.m.
It would depend very largely on the situation at hand, but such an event could be viewed as a Guild Bank Theft, which is part of our Scam policy. It would be best to avoid these sorts of situations by limiting access to your guild from the lowest rank, so you are unable to accidentally invite an individual who may take advantage of the situation.
There are many factors that are considered when investigating these issues, and you may want to check out our Scam policies for more information.
Scam Policy http://us.blizzard.com/support/article/20459