Do not underestimate the chances of a video of your new kittens getting shared amongst tens of people. Or the impact that those uploads would have on your dodgy 3G connection.

It makes sense to host stuff you want to share on sort of server in a data centre somewhere, even if you think of that server as basically a cache.

And no, I would still have no internet access when I was in a train tunnel, even if there had been a big push behind this sort of hosting.