Well there are 2-3 scenarios here:
1st
You "fall in love" with a person on the internet, but never see her/him in real life.
I don't see this as real love, since real love IMO has to have a physical aspect.
2nd
You "fall in love" with a person on the internet, AND see her/him in real life.
Here I think the real love first will occur when they actually meets each other.
3rd
You "fall in love" with a person you know, get together with her/him, and the person have to go away, so it turns into a long distance relationship.
This can only work if the two really love each other.
EDIT:
This is only my honest opinion! and of course there are exceptions in the 1st example!