Celebrities: They're just like us. As in, they know when we're trying to take sneaky photos in public.
This actually seems like a successful creepshot. Naomi Watts is staring at her phone, listening to music, and just generally lost to the world. Of all the elements of successfully taking pics of unaware celebs, this seems to have all of them. Audio-visual distraction, the magic of the subway where nobody is paying attention to anybody, a seated subject.
Hell, it turned out pretty good. Check it out.
And here's Watts' picture of the picture-taker. Bam! When did she even capture that? It must have been by moving her hand just so to capture the creep during the shot. (No shade against the person who took the original photo, creep is a term of art in this case.)
So this raises the question: When is it ok to take pictures of celebrities? My personal view is that we have to play by professional photographer rules. That means walking up to them and getting their permission first. That also means that you'll have to broke the unspoken rule of never talking to celebrities, which is a huge no-no.
In fact, the only acceptable time to photograph a celeb in public is when it's Danny DeVito and he's walking a dog in a dress. A high standard but I don't make the rules. (I do, in fact, make the rules.)
Oh, all of this is null and void if you can convincingly "take a picture of your friend" with the celeb in the background.