Speaking as someone who photographs shooters, catching brass in the air still never fails to make me happy.
Whether it's just exiting the ejection port...
...or making a pretty rainbow arc in the air...
...it never fails to elicit a smile. But if I were shooting a dude firing a carbine and then chimped the back of my camera to see the sight that greeted A1C Andrew Sarver in September of last year, I'd have come pretty close to decorating my cupcakes right on the spot.
That overgassed M4 sent the brass spinning forward to the shooter's two o'clock, and Sarver got the money shot.
Because it's been discussed so much, it's pretty highly placed in Google image search results for "M4 carbine". As a matter of fact, when I did that very image search to write this post, it's the highest-placed photo that actually shows a person firing an M4. As an added bonus, it's a .gov photo, which means it's public domain.
Which means that forever more, whenever some hand-wringing journalist is searching for an image of an M4 carbine, they're going to stumble across this handy, dramatic, free-to-use photo. Now, maybe they think that's actually something coming out of the end of the barrel, I don't know and it doesn't matter, because they're going to use it because it looks cool.
And when they use it, every smooth-brained gun dork on the internet comes bouncing out of the woodwork to show off how much they know about guns. "HA HA LIBTARDS! GUNS DON'T SHOOT BRASS! FAKE NEWS! PHOTOSHOP!"
I hate having to start the day with a headache...
.