Theft is a big issue for shared storage (I believe EVE online even promotes it).

However, I think the benefits are greater than the risks. PLus with just a little bit of security management, the theft can be reduced. If theft does occur, then the security measures reduce the impact to the guild.

Again non of this is ground breaking. All of these things have been done before, and are now pretty much MMO basics. SE just needs to give us these features.