Does using phones ruin gigs?
Bands like Alt J have said they're really frustrated when fans film at their gigs because it can ruin the atmosphere.
Gus from the band says: "I really want to say on stage sometimes, this is our last song, just put down your phones and enjoy it and remember it."
"I'm not even sure what people do with that footage, it probably looks and sounds really rubbish."
And it's not just Alt J who feel that way. At Radio One's big Weekend in Northern Ireland, lots of people were filming acts.
Big names like Jack White and the Yeah Yeah Yeahs have even put up signs at their gigs asking people to leave their mobiles in their pockets.