Following "Dropbox JavaScript SDK vs Dropbox saver JavaScript" I can tell that Greg's solution there is not robust. The order of the script tags makes a difference, and some functions inside these libs don't work no matter what the order is, for example:
Uncaught TypeError: Dropbox.isBrowserSupported is not a function
Why isn't don't the libraries use a more robust namespace technic, at least use a better name than Dropbox for the global variable?