I don't think its possible to truly fall in love with someone online. And I do not want to belittle the experiences of anyone else here but the reason is you have to see the person and spend time with them to know if they're right for you. When we say 'fall in love', I'm thinking of the kind of love where you're prepared to spend the rest of your life with that person and commit to them unconditionally, not just a strong liking, a crush, or an infatuation. You can't know that 'love' is going to happen until you've spent considerable amounts of time with a person, which is impossible online. It's not even an emotional question it plays out as pure logic in my mind.
And without getting too graphic, if we're talking about a true relationship, you have to have some kind of sexual energy going on there. If two individuals cannot be comfortable with one another (to a certain degree, doesn't have to be this explosion of.. whatever.. every single time but, you know, at least a 'healthy' physical and emotional relationship) then these people will always have that rift between them, this distance, and the knowledge that something isn't qutie right. In principle I'm sure some people would say 'yes but we'd work through that'. But its often overlooked and underestimated. Don't forget it is the main reason many marriages break apart and infidelity occurs.
I just think that, in the relationships I've had, the love I felt for that person at its very strongest was not something I could have created online because it took time to develop. It's like asking, can you grow a 300 year old bonzai tree in a matter of weeks without water or seeds. Sure in principle anythings possible I suppose, but really, can that be done?