Well, stealing from guildguards will cause them to attack if you fail, not if you don't, and they will yell you are attacking the guild even if they start the fight. So, like stealing from players, you do it successfully you might get away with it. And the only shoppie, in galadon at least, has some other major downsides for trying to steal. But I really doubt you should get flagged for stealing from guild guards or shoppies. Though if memory serves, there is a couple round about ways that could get you wanted for just standing in the wrong place at the wrong time.