In my own mind, I believe it is possible to fall in love online, as it has happened to me, and to my father.
But as neither I nor he have ever met the people with whom we believe ourselves to be in love, there is no way of knowing if we would still love them if we actually met them "in real life".
So you may be right, it could just be an illusion.
On another note, it isn't always a good idea to fall for someone you may never meet. It can be quite a painful experience.
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Effect of Blood Plasma from Psychotic Patients upon Performance of Trained Rats