> Email is quite clearly a thing that needs fixing
Honestly, I've never seen it that way. Email continues to work fine. It's platform independent and easy to use/setup. It's probably one of the best things on the internet ever.
Email is great. But long threads with various forwards and cc's become incredibly painful. Gmail have gone some way to fixing it, but Fluent.io looked like they were doing a great job (Judging by the demo videos)
Ever tried sending an attachment to someone over 4-5mb? One of the most broken aspects of email right there and something that won't be changing any time soon. Sure you can use a service like Mediafire or Rapidshare, but it's just another step that shouldn't exist in this day and age.
Dropbox should allow you to send a shortcut to a file (on dropbox) along with your email so that the recipient can just grab the file when they actually want it instead of clugging up the email systems with useless junk.