It's possible to fall in love with the idea you have of the person you're talking to. When infatuation happens online, your mind disregards potential negatives relating to that person. There are lots of aspects of someone that simply don't show up on the computer no matter how often you talk on it. It's just that you mentally fill in the existing blanks with nothing but good things, even though that's often not the reality of the situation - and those blanks may well prove to be dealbreakers in real life.
So yes, in theory it's possible, but be prepared for a whole lot of unforeseen extras if and when you meet. Having said that, at that point there's often such familiarity and a desire to make it work on both ends that the bad gets overlooked. With so much build-up and emotional investment having gone into it, it's guaranteed to work in many cases. Though of course, there are exceptions to every rule, and it's still common enough for two people to meet and not get along at all in person. I guess it comes down to whether both parties are equally motivated to make it work out - and whether or not they represented themselves fairly online.