Dropbox Dropping Support for Older OSs Soon
I just got an email from Dropbox letting me know that as of November 3, new installations of Dropbox will be no longer be possible on macOS 10.6 (Snow Leopard), 10.7 (Lion) and 10.8 (Mountain Lion) and Windows Vista. Then, on January 17, 2018, support for these OSs will be discontinued entirely. There is more here at Dropbox's site.
I know some iTunes users like to store their libraries in Dropbox (which I don't think is a great idea, but there it is) so if you've got media files on an older machine using Dropbox you may want to move that stuff out of there.