&gt; It&#x27;s because decentralization like that is stupidly, <i>stupidly</i> inefficient.<p>Disagree. If you&#x27;re Netflix wanting to distribute Jessica Jones then you want something like a CDN (although in that context BitTorrent is also &quot;something like a CDN&quot;).<p>But think about wanting to share photos with your friends. There are only thirty people who actually want to see the photos. Twenty five of them live in the same city as you, which makes direction connections to you about as efficient as a local CDN node, and the other five live in four different cities, so in all but one case there is nothing to be gained from caching in any of those places because there will only ever be one copy requested. In that one last case the CDN would conserve just one long-distance copy, and that&#x27;s assuming we can&#x27;t make P2P software smart enough to have the second person in Timbuktu get the photos from the first person there.<p>&gt; we&#x27;re not on IPv6 yet<p>This one is probably the main reason why this hasn&#x27;t actually happened yet, but it&#x27;s not like we don&#x27;t know what to do -- how about we get on IPv6 already?<p>&gt; or that people also use cameras<p>You seem to be implying there is some reason why a photo taken with a camera couldn&#x27;t still be distributed using a mobile device (or plug server or PC or whatever you like).<p>&gt; or that they change their phones<p>And then they can copy the stuff from one to the other.<p>&gt; Not to mention that the assumption that your phone is actually on-line 24&#x2F;7 is unrealistic<p>Availability is a different tack. OK, your phone doesn&#x27;t have twelve nines of uptime, but it probably is actually online upwards of 90% of the time. And we know how to build reliable systems out of mostly-reliable pieces.<p>We&#x27;re assuming that there is a piece of software on your device which already knows who your friends are. So now it just needs a check box that says &quot;cache things for my friends if they cache things for me&quot; and now your friends can get your photos from your other friends (or from their own device) even when your device is occasionally incommunicado.<p>&gt; or simply want to free up space on SD card for something else.<p>I think there&#x27;s a law of physics that says your photos, to exist, have to exist somewhere. I suppose &quot;I would rather give my private data to Facebook than buy an SD card big enough to hold it&quot; is the sort of thing you have to decide for yourself.