Hmm,interesting topic. As for me, i'm a man utd supporter through and through. Been supporting them for about 10 years now. Truth be told, of all the big 4's in the EPL, every team has its "specialties" in my opinion, Arsenal with beautiful football, Liverpool with their supporters, Chelsea for their style and Man Utd with beautiful football,style and great supporters! . But i always keep a look out for West Ham games, they're one of the teams which i really enjoy watching them play. So i do think that one can support more than one team at a time, its just a matter of how MUCH you support it. For me, it'll always be Man Utd first and foremost. If its West Ham vs Tottenham,i'll be rooting for West Ham.

My humble 2 cents