I have about 14k people and 7GB media. I tried Dropbox and One Drive, but found that the response times were inadequate. FTM writes continuously to the family tree file, so One Drive is constantly trying to refresh the 100+MB data file. I settled on One Drive, but I use is as a backup rather than a real-time cloud service. I have Office 365, which is $100/year and in addition to Word/Powerpoint/Excel also has 1 TB of storage. Backup files with media are generally too large to upload. But, I load up my media directory and the data files separately. None of my media files are more than 1GB individually. I use a desktop and a laptop, so this approach keeps both with ready access to all the files, and also has sufficient responsiveness.