Dropbox has had a number of security concerns[1].

Dropbox is headquartered in the US and is subject to US law, and interpretations thereof.

Dropbox has a history of taking on US government bureaucrats for roles in the company, including members of the US Intelligence Community[2].

If any of these clash with your threat model, look elsewhere? Syncthing[3] might be your thing.

1. https://en.wikipedia.org/wiki/Dropbox#Privacy_and_security_c...

2. No link, because someone "sterilized" Dropbox's Wikipedia article of those particular controversies.

3. https://syncthing.net/