I was an early adopter of Dropbox. However, I found that Dropbox's high usage of bandwidth precluded its use when I spent several months of 2011 in Europe with only a sparse 2 gig PER MONTH internet allowance.

I ended up by installing my own internet-accessible file-server. This also had the advantage that my data wasn't being controlled by an external entity with dubious privacy concerns.

I just got an email, that ntfs under linux won't be supported any longer. So you can no longer share a Dropbox partition in dual boot systems. Or am I supposed to mount ext4 under windows?

I just started testing Keybase filesystem. Looks promising so far. Everything encrypted, 250GB for free (for now). Sharing folders with my coworker works seamless.

The advantage over Dropbox is that it does not take any space on your harddrive. Also everything is encrypted by default.

A disadvantage is that your data is not available without internet, since it works like a network drive.

https://keybase.io/docs/kbfs