I do believe I completely left out that I only 'point out' someone who is making me uncomfortable by giving him the watch command if HE hasn't seen it first.. which he usually does. He is very good about picking out people, he will keep an eye on them until they're long gone...
It was said several times here though, that obedience scares people the most... I think Stark was a perfect example of that, because they immediately think a dog who listens to you the first time is an attack dog or something.. My old bitch wouldn't hurt a fly, she's the one who had the 'watch' command down so well, she never bit a human in her life and never acted like she wanted to. She has a sweet temperament and a soft, feminine face.. But if I was out alone with her and someone was making me uncomfortable all I had to do was make her focus, heel, down, back up, and keep going and the person in question would usually back off.
Because my boy walks in a beautiful heel and immediately stops and/or sits when I stop, I get asked so often if he's a police dog, K9, or if he's a trained attack dog or if he is going to bite them ("Not if I don't tell him to

")... People's ignorance is your best tool.
While I openly admit I teach my dogs an alert/watch command, just about any GSD/large dog itself tends to deter people from trying something with you.. Heck, I was standing at a redbox the other night with my dummy, I had him sitting between me and the redbox machine holding his traffic lead by the loop near his collar.. A man came up to get in line, saw J and went and got in his car until I was done and left, then he got his movies.
The breed's reputation itself is usually enough..
And - well my version of the watch command anyway - the alert command is not to get an aggressive response. I know the difference.. While walking my pup earlier this morning there was a boat out in the water, I told him to watch it, he did until I said "Okay(which is his release command), good!"
He wasn't afraid of the boat, he wasn't reacting to the boat, he was keeping his eyes on it like I told him to.
I also will use his flirtpole to reinforce it, making him stay and 'watch it' while it moves about.