I use Dropbox as my main mode of sending files and I prefer to receive them via Dropbox.
As Keni said (and I can confirm after probably a hundred or so transfers at this point) there is absolutely NO need to download and install the Dropbox "app". Nor does the recipient. They try to make you THINK that but it is not true.
I installed their uploader thingie when I first signed up and removed it immediately because it slowed down my system and just generally creeped me out (it seems to always be hunting for files to upload or doing other weird crap). I have wiped this system multiple times since I removed it so I know it is not just because it is working in the background.
All you need to do to upload is sign into your DP account, click the Upload button, use the Choose Files option (which opens a file explorer... usually to your desktop), select any files you want to share and click the Upload button (or whatever they have it labelled).
Wait for the upload to finish and then to send it you just hover over the file to expose the "Share" button. Click that and it will give you the option to email directly and will also generate a link that you can copy paste into a message manually. Of course I just copy the link and send it (I would never plug someone else's email into one of those things). I have never had any complaints about the links not working and I've dealt with many non dropbox users. It just downloads normally in their browser as a regular file.
I HAVE had issues sometimes when receiving links other than a wave or bundle or compressed file or whatever where sometimes the link will try to open in the dropbox preview window. Not sure what the senders have done to make that occur (and it isn't desired behavior for something like a project file) but most times I just get a downloable file that I can do what I want with.
As to the OP... seriously I would NOT use any automagic online syncing options/apps... especially on a DAW. Best bet would be to just back up and upload manually or get a good external drive with a hyper customizable backup/sync program then upload that manually to the online storage site.
Also remember if an online storage site goes tits up or their hardware fails and that was your only back up your are shiz outta luck just like a local storage failure. Multiple drives and online storage and whatever else you can conjure up (like discs for more important projects and or storing drives in another physical location like a friends house in case of fire, theft or whatever) is really the way to go for the ultra paranoid/vigilent. Not always practical though so you just gotta do risk assessment based on your own needs.
Those consumer auto online backup dealies though (or even the programs for local drives)... not great for a DAW. You don't want anything waking up, hunting around or generally futzing things up while you work. You could look for details on a "Suspend/Disable" type function so it only activates when you aren't working.
Cheers.
Edit: And of course I just jumped to a bunch of assumptions about what the OP was asking based on the thread. It's cool you can set it up as a save option for Sonar but I still personally wouldn't go that route (just because I don't want to take any resource hits and don't mind uploading manually). As for file corruption... I have no idea.