JUSTIN BIEBER didn't really think this one through.

--During recent show, a fan threw her phone onstage . . . and Justin picked it up.  Instead of immediately giving it back, he decided to have some fun with it.  (--We're assuming it was a GIRL'S phone.)

--He took photos of himself and the crowd with it, which caused the girls in the audience to SHRIEK in excitement . . . and was probably a HUGE thrill for that lucky fan.  Pretty cool, huh?

--Well, there's just one problem:  It set a bad precedent.  Suddenly, a bunch of girls were throwing THEIR phones onstage.  Justin realized his mistake at this point, and didn't want to spend the rest of the night screwing with people's phones.

--He playfully scolded the crowd . . . saying quote, "Hey, no!  We're not just going to keep [throwing] cell phones up here, and expecting everyone to just get pictures of me.  No.  That's not how it works.  I'll never do that again, so don't even try it."

--But of course they DID try it . . . and cell phones continued to hit the stage.

--Justin went on, quote, "Hey!  We're going to have a bunch of iPhones and I'm just going to take them home . . . No!  I'm not touching your phones . . . Get [these] phones off the stage, guys, c'mon.  I'm literally going to just break your phones.

--"You guys want broken phones by Justin Bieber?  I'll do the honors."

--He even KICKED some of the phones away . . . although some pro-Justin fans on the Internet claim he was only PRETENDING to kick them.

(--You can find video on YouTube.  If that video is down, you can find it at TheHollywoodGossip.com.)