To me, "in love" is just a way of saying you're totally infatuated with that person and you can't stop thinking about them. That doesn't mean you'd throw yourself off a bridge for them, just that you think they're super and you get butterflies just looking at them.
The word "love" gets thrown around a lot... that's why I make a very big distinction between "love" and "Love". I love key lime pie- I think it's fabulous. However, I Love Martel, and would throw myself off a bridge to save his life without hesitation. Needless to say, I don't feel the same way about key lime pie.
I have been "in love" with pairs of shoes before- thinking they're fabulous, wondering what they'd look like on me, finding myself daydreaming about where I would wear them at various times of the day. However, I have only ever been "in Love" with Martel- that kind of insane spiritual connection when you've been having amazing sex and are both in the middle of having an insane tantric orgasm and your bodies are wrapped around each other and you look in each other's eyes and suddenly the whole universe is wrapped up in those few, precious seconds when you see someone for the cosmic being that they are. That, to me, is being "in Love".
That being said... I love key lime pie