In an age where Skype is pretty much universal, I think it's definitely doable. It probably helps that they're both pretty shy people who don't really need sex
Two things. First, Skype is not universal. It has ~660m registered users, among which there are probably 5-10% inactive accounts, 1-5% corporate dummy accounts, and 2-5% repeat or reregistered accounts, which would bring the total amount of users down to something like 580-600m. That's still a lot of people, but there are over 7 billion people on earth. That's 7 with nine zeros after it. Hardly Universal. Universal would be Microsoft Windows (which ominously enough, owns Skype).
Second, they're shy and don't need sex? More like, they're shy so they cope with not having sex. Sex is a basic biological requirement. It's hardwired into us, like eating and shitting. Denying that need is a good way to repress your humanity. As an aside, there are a very small minority of individuals who are truly asexual, but this is rare in the extreme.
Someday they plan to meet, even though they live on opposite sides of the country, but it's been going pretty well so far for them.
Lol! Believe me, I've contemplated that existence. It's easy to say 'yeah I have a girlfriend/boyfriend' as a way of getting out of social engagements, even though you've never personally, physically met your SO. Further, this type of behavior, wherein a shy, net-centered individual makes meaningful connections solely though the internet, is highly irregular and unstable. Google closed shell syndrome for a highly accurate, albeit fictional account of what the internet can do to people.
As far as the original argument goes, here are some additional points. Something like 90% of human communication is nonverbal, meaning that the majority of what you communicate to your significant other is not encoded in the words you speak. That 90% includes tone of voice, body language, eye contact, appearance, volume, whether or not you are directly facing the person, and scent. On the subject of scent, let me say that pheromones are real. Humans release pheromones that other humans can subconsciously smell and pick up on. This plays a large role in forming relationships, particularly casual hookups. Barflies get good at determining who is in the mood, so to speak, by their scent. There's something that you can't get over skype.
Anyway, my opinion is almost exactly the same as it was on page one (if you can't tell).