yes, they can work, even if you haven't met in person or it has been/will be a long time before you meet. but...
you have to establish a foundation of trust, honesty, integrity, compassion, and tolerance.
i think some of the pro's are that you get to know the other person in ways you wouldn't if you were together. you have to establish very good communication skills because you can't rely on body language or facial expressions, so things can be taken out of context very easily. you have to get to know each other's style of communication and both adapt to be able to relate to each other. but the result of this is learning things about each other and in ways that aren't often found in 'face-to-face' relationships.
you learn to love and like each other for who you are emotionally, spiritually, intellectually, and in so many other ways, not based on physical attraction. we often say we don't care what the other person looks like, but when you're in a long distance relationship, you find out quickly if this is a truth for you or not.
i think the biggest con is the lack of physical touch. it's very hard to be so close to someone emotionally and not be able to touch them. we need touch in our lives, esp. with people we care about on intimate levels.
can it work?? yes! will it work?? that's a choice you both have to make individually AND together. it takes a lot of commitment to overcome the obstacles, but if you really care, you'll find a way.