For some time now I'm a happy user of Dropbox. Dropbox is basically your personal hard drive in the cloud. I'm using it to store a large part of my personal files. Dropbox works via a website, but you can also approach your files via Windows Explorer (as your other files categorized in folders).
Recently I had to move my Dropbox folder to a different part of my computer (corporate disk quota problems...). After thinking it through a bit I thought: Ok, I can just copy this folder to elsewhere. If things go wrong I'll still have them in the cloud (because Explorer syncs my files with my files on the internet/in Dropbox). So I copied them and everything seemed to be OK.
But every now and then we have a corporate sync tool making sure your corporate files can be accessed everywhere/everytime when you disconnect your laptop from the next. This sync tool did his job and because I copied the files it thought: Ok, I'll just delete them all as you wish.
Even more painful was the fact that someone had shared two folders with me to collaborate on some files. These were gone as well...
A bit of panic broke out then... All my personal files are gone! What happened?! I know and understand now that I should never have COPIED those files, but I should have MOVED them. If you go to Dropbox 'Preferences' you can easily see the current Dropbox folder location. And just behind that location there's MOVE button... Using that button makes sure the folder copying goes OK and you don't loose your personal files.
Oh, and how did I get my files back? Well IT makes snapshots of my drives every hour and saves them for some time. I was able to find the right snapshot and copy my files back to the Dropbox folder. Hooray for our IT department!
Hope this helps.