I use the Skydrive "cloud" (now called Onedrive as of last week) from Microsoft. I have used FTM 2012 on my desktop computer for the last couple years. When working on my laptop I had resigned myself to using the online tree (as we all know FTM is a lot more robust than the online tree). I recently decided to try to copy all my FTM files into my cloud to see if I can use FTM on both my desktop and my laptop.... here is what I have.
My desktop computer syncs with the online tree
My laptop computer access the files that the desktop creates without an issue
.... well there is ONE issue!!!! You have to give your "cloud" files time to update or it messes up the entire situation!!
If I am working on my laptop and close the program at 10:02 am, it can take some time (amounts can very depending on internet speed and your syncing choices) for the files to update on my desktop computer. If I open my desktop program BEFORE the file has been updated this will create a big problem. The laptop now recognizes "our family tree file" is being used so makes a SECOND copy with a slightly different name.
So while using the cloud for FTM works wonderfully, and makes my genealogy efforts that much easier, you do have to be careful or you can make a mess for yourself!