Dropbox is constantly being improved, one such improvement is that it randomly opens a window to tell you "you can right click on a folder and click make available offline" or other such handy tips (occurs on mac and windows).
(ၜᗝ ၜ)
The idea is to add a preference setting to disable this, for people who do not want pop-up-ads (or equivalent), as this feature was added without the option to not have unwanted invasive popups.
⊂(´・◡・⊂ )∘˚˳°