Ezsme, every guild has a bank so you can be in five and if you have access to the bank you can put in and take out whatever you want in any of them. Guild banks have always had to be one of an honor system because of this. Some games have better controls than others, like multiple tabs that can each have different access, but ESO is one huge list of stuff.
As for spies, if you put an EP toon into campaign A, you cannot also put your AD or DC allied toon in the same campaign. So there is no way to physically spy that way unless you spend the money for multiple accounts. Now via the multiguild chat - you can see all guilds you belong to at all times - and whatever goes in voice chat, you might be able to pick up info and pass it on. Again we are back to an honor system and not everyone has a good honor system.
Look at history, we've had spies for wars for thousands of years. Why expect a game to be any different? It's played by humans. =)
» Edited on: 2014-02-20 12:45:53