How legitimate do you consider the relationship? Have you ever met in person? Do you actually know him well? If not, it may be that he's uncomfortable bridging that gap between virtual sex buddy and genuine girlfriend. Maybe he fears rejection if you meet face to face. Or he might consider the relationship far more trivial than you do, as others suggest, which would be quite selfish. Or worse, he could be hiding something, like that he's married. Instead of asking what kind of man this is, I would ask him why he refuses.