Originally Posted by Jovimimi

...I will never in my life forget the response to Richie's I'll be There For you in manheim 2003 ... the crowd sang 'alone' without richie without him asking for it it was a chant to keep the song going it was one of the most impressive audience reaction ever ... Jon couldn't stop it by beginning a new song like he usually do so he had to sing along with the crowd and then he managed to get the control back ....

that sort of reaction is maybe what was the OP refering to and if it is not mandatory to all show in europe it is much more common here and it's rather well known that artists LOVE that