I've not played a pickpocket, but I believe they can clean you out with you standing there. Steal, deft touch, and warning skill, which will stop the steal if it would have failed are probably enough to prevent failure...maybe ever if mastered.
I've heard you want to perfect steal before you learn deft touch as it is very hard afterward.
Blackjack is very reliable from my experience. I've taken it on some thugs because of how better it is than weapon-butt BJ. I'd say BJ is about 75% or better once perfected. Can depend on head gear of the victim, though.
Of course, everyone hates people who steal.