I am terribly sarcastic but I have learned to hold my tongue most of the time. A lot of people don't get that sort of "humor".
I am also more keenly aware of my audience than when I was younger. Smart-alecks tend to find each other;that's been my experience.
Personal comments aren't usually ever welcome, but general topics can usually do with a dose of sarcasm. Again, being aware of your listener is key.
In relationships, it tends to become a weapon, so it is best left off the menu when discussions are in play. No point hurting anyone.