I've been trying to work out the answer to this one. The only common ground I have been able to identify is that the songs described as anthems are often powerful tunes which ramp up the power from verse to verse. I don't know a lot about modes but I suspect that a lot of them are written in specific modes which emphasise the power of the tune. Often I think they change key upwards as they progress, as well.

Last night on the Oz tv show, Australian Idol (the search for new Oz singing talent) one of the contestants sang a song by Johnny Farnham (who he is is another very long story - I think he's a weedy little wannabe who has somehow managed to con the Oz public, but who am I when I am at home??) called You're The Voice. It does have that sentiment referred to by alanabit, but its main claim to fame is the powerful style of melody which gets bigger and more dramatic as the song progresses that leads to people wanting to sing along and wave their arms in the air.

Well, most people. Not me. It makes me want to wave my fingers in my throat. ;-P

Helen