Chicken and the egg
I like the chicken and the egg comment.
I've always wanted things like HD Voice, HD Videoconferencing, 60fps online TV services, and at least 30fps remote desktop (a.k.a. splashtop)
These things all somewhat exist but aren't very mature because not enough people have access to sufficient bandwidth to make it worthwhile.
I mean, even something like online gaming, we could probably get much better experiences if we had guaranteed 10ms latency to many popular servers. Once superfast connections get popular, developers have a reason to optimize their apps to take advantage of super responsiveness.
It also forces ISPs to build more backhaul to more places. Right now, I have no faith in being able pull more than 4-5mbits consistently from servers that aren't in some efficient setup that puts servers close to me (like netflix or youtube).