I was being a bit idealistic, but in theory that's the story.
Yeah, xkcd handwaved away a couple of other solutions too: use a chat client to transfer a file? "no-one uses this obsolete one!"; use a file upload site? "I'm scared of porn popups and they don't work properly anyway"
The problem isn't 'sending a file', it's 'peer to peer communication', which is hard without an intermediary and/or shennanigans due to ubiquitous NAT. I image in the everyone-has-an-IP universe of ip6, this will no longer be an issue.
A 50% divorce rate is not a 'failure' rate. People change and move on - in some cases a divorce is an overall win-win situation, not a failure. Slavishly staying together because of obligation is a failure.