What kinds of web-based services will be popular in five years that don't exist today (or at least aren't popular yet)?

If I had asked this question in 2000, hopefully someone would’ve said:

“A video-sharing service where you upload your favorite home videos (or even recordings of TV episodes) and let anyone using that website watch it for free.”

And in several years, up came YouKu! (for the Chinese audience, at least. You know what it is for us, but here’s a hint: It’s often abbreviated to “YT.”)

But from this year, what kinds of web services that do not exist today (or at least aren’t common or popular today), will be popular in 5 years?

And why do you think so?