I believe in love and I believe in infatuation, and I don't believe in the two being the same thing.
Infatuation is a feeling - that bubbly, cutesy sensation that makes you want to giggle and snuggle up in someone's lap and have their fingers play with your hair. (And sometimes it's that wrenching feeling in your gut that keeps you up at night thinking horrid, jealous thoughts.) Infatuation is an impermanent, come-and-go feeling; love is not.
To love is simply to want the best for somebody else even (some might say, especially) when it means doing something that is difficult or unpleasant for you. Love is to have one's own happiness dependent on another's. So if someone I love (whether it's my boyfriend, my cat, my dad, my grandma or my best friend) is unhappy, I am unhappy. If they are happy, at least some part of me is too.
As Massive Attack so eloquently put it:
Love, love is a verb
Love is a doing word
P.S. I believe one of the big reasons people can't seem to keep their marriages together anymore is because most of them didn't marry for anything but dramatic infatuation in the first place.