All I can think of are Dropbox and (the wretched) Google Drive<p>Looking specifically for:
- Security
- Availability (no downtime/problems)
- Compatibility (linking/integrating w/ other apps)
- Ease of use (upload, download, etc)
- UX
- Mobility
Probably a minority opinion here but I've been strangely happy with MS OneDrive. No official Linux client though and limitations on max file size, but it's been solidly reliable for the past few years for me.