There are many articles, which I have read over the years, where they have issues of storing "personal" files and some do not like the use of cloud systems unless it uses a heavy duty encryption system for the whole process, including during the upload/download process over the Net.
To be honest, with all I have read, I do not "trust" Cloud services that are not located in and administered by the business IT department.
The need for a "secured" WiFi access point is another drawback. I rarely am able to find any WiFi access where I need to use my laptop, or tablet, outside my home/office network. The only access I have outside my apartment is my own WiFi network, when I place a secondary access point so I can use it in the common area[s] 10 floors below it in living room window.
Actually, with Ubuntu having a Cloud version, it might be easier to setup your own Cloud service in your home/work environment so can "trust" the service.