Very frequently magicians will post in social media groups that they don’t understand why people want to show them magic tricks. I’ve got no problem with that, and unless it’s at a totally inappropriate time, like in the middle of a formal show, it let them.
I think the reason for this is that magicians have ego problems and they can’t let the spotlight on someone else. Usually it’s a trick like the 21 card trick and it won’t remotely step on anything you’re doing. You can get some great moments out of it, like immediately forcing the card they failed to find if the trick doesn’t work. The key to doing something like that, is acting like it just happened, so it doesn’t look like you’re one upping the person.
I’ve seen some crazy things that I never expecting, like a old guy that did a perfect tabled faro shuffle with my old beat up deck of cards! I then spent the next half an hour with him teaching me the basics of how to do it. Or this guy:
That guy also taught me the basics of ripping a deck of cards in half, and with the help of my friend Todd Gardner who is a strong man I can now rip a deck of cards in half!
Your job is to be an ambassador for the event you’re working, and with that in mind I almost always say YES when someone offers to do a trick!