i actually do a&r now and let me tell you....
more than having a good ear, artist and repertoire is a more complicated thing than being able to hear a star...i wish it was that simple...
a&r people are basically business to business direct salespeople.....in that...you're seeking talent....then once you have the talent...you're negotiating what amounts to a memo of understanding....basically stating "what if i do get signed, then..." terms.....then as a&r, you're basically risking your career on if that person is going to waste the label money through the necessity for development or if the potential artist is closer to being ready...
you wont get blackballed in the industry..but you can get fired easy.....
a lot of times...lawyers act as a&r when they're shopping a demo (which is the ONLY person who should ever be shopping a demo)
basically you become the liason between the label and the artist....but....
getting in as a&r is a peculiar vessel at majors.....it's definately not the kind of thing you go apply for...a lot of times a&r are former washed up singers, musicians, engineers or in my case...started as an intern and stayed affiliated long enough.....
oh the other bad part about it is...it's always comission based...so if you need loot all the time.....like major loot....then you have to be on it constantly....
if you're young enough...go intern at a label for a few months..express interest...and pray somebody gives you a shot...
good luck