Yeah... I guess it just depends on the situation. I don't typically want to bother people.
A couple years ago I saw Nate Robinson at the movie theater in the same building as my office, but didn't bug him because he was with a group of people.
A couple weeks ago I was at dinner with my girlfriend and say Jay Pharoah sitting at the bar as I walked out. I came very close to saying something to him, because I'm one of the few people who watches SNL religiously, but he was macking on some girl and I didn't want to interrupt.
A couple years ago I was at UCB Theater in NYC... I showed up late and the only tickets they had left were standing-room only. I was standing next to Zach Woods (from "The Office" and later "Silicon Valley") and like 8 ridiculously attractive girls hanging all over him. I didn't bother him. I thought it was funny that a guy who plays such a nerdy character was surrounded by tons of comedy groupies. I remember thinking to myself... "This guy f----s"
On one work trip, I was walking outside 30 Rockefeller Center on the way to a sports bar to catch a Celtic playoff game... I saw Seth Meyers run out of the building desperately looking for a cab. I happened to remember that Seth Meyers is a Celtic fan, so I shouted out, "Seth... Go Celtics!" and he gave me a knowing nod... I assume the dude was probably heading somewhere to watch the team too. If I had more guts, I would have asked where he was watching the game. Lol.
I saw Shawn Kemp hanging out at a bar in Seattle that I later learned he owned. I was with my best friend who is a hardcore diehard Sonic fan from birth... and I could see him freaking out... so I went up to Kemp on my friend's behalf and we got pictures with him. But then a few months ago I saw Detlef Schrempf in the lobby of my office building standing by himself, but I didn't want to bother him.
When I drove up to catch the Blazers/Celtics game a couple years ago, I was in an elevator with Fab Melo and Avery Bradley and briefly talked with them and wished them luck. My friend come down a couple minutes later and I saw him get out of the elevator with Paul Pierce, but apparently he was too starstruck to say anything. I would have liked to have talked to Pierce, but I wasn't going to chase him down.
Just depends on the situation, I guess.