For those that don't know, Megaupload was a file sharing site that was in the top 100 largest websites until it got shut down in 2012. It had over 50 million daily users.

The guy who made it (Kim Dotcom) is now relaunching it as Megaupload 2. But this time, every file transfer is linked to a Bitcoin micro-transaction.

Here's their video about it: https://www.youtube.com/watch?v=yPGdilknFbc&t=0s - this could be what takes Bitcoin mainstream.