I supported United from young age, living next to the ground and seeing the odd game. However, when I went to school in the Alty area, I met mates who followed Alty, went to a few games, and now get to every game I can whilst still supporting United. If Alty played United in the FA Cup then I would back Alty, because of them being underdogs and relatively less successful in the tournament. I think you can follow as many teams as you like, it's just up to you who you support when they meet. Also, I reckon there are lots of reasons for following a team - I look out for Fiorentina's results because they beat United once and played really well, and I really loved Batistuta; I look out for Auxerre because of their performance against Arsenal in the Champions League and also because of Guy Roux being a legend; Hamburg because my dad used to work there and told me about their old team, etc. It's not always so simple as supporting one team all the way, although it is possible and dedicated. Either way you're just enjoying football.