yes, additional from that:

yes, there are many who support many teams at 1 time.
For example, I support A team, but at the same time I'm enjoy watching B team and C team playing their nice football, am I support 3 teams? Hell no, enjoy watching and support the team are 2 different things but many think it is a same thing.

as air_mood said,
we no need to watch a % of games then only considered as real fan. I myself never watch all Man Utd's matches, esp those at the midnight but I get the result as soon as I wake up, am I not consider a Man Utd fan?

regarding to Soulsareworthless,
Club and National team are different