Why? Because he might smash it, kick it into the crowd or yell at you in front of thousands of peeps!
Just ask fans at his second-night show at Madison Square Garden.
When a front-row belieber threw her cell phone on stage, Justin quickly grabbed it and began snapping pics of himself and the crowd!
His fans went nuts, of course, and instantly started throwing their phones on stage too!
The copycats seemed to frustrate JB and not only did he kick the phones back into the crowd but he said he'd never grab a fan's phone again! LOL!
Lucky for us, the whole moment was taped and put on YouTube for us to see! Peep the entire thing below!
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