Are there safer alternatives for dropbox? As someone who knows my mailadress basically only is a password away from my personal data.
2 Answers
You should be able to use Two-step verification instead - you then need your mobile phone or another device to sign into Dropbox:

Go to https://www.dropbox.com/account#security, and you can enable it. You can find out more on it here (note the 'advanced' section for Linux users - guess what I'll be trying later... :D ).
Also note that, the best thing would be to have a really secure passwords (you can generate some nice ones with cat /dev/urandom | tr -dc 'a-zA-Z0-9' | head -c 20), as well as using different passwords for different sites, especially with the same email.
And perhaps also check from where Dropbox has been/is being accessed under the the Dropbox Security tab:

You also may want to enable these Email Alert options under Dropbox's Profile Preferences:

- 30,732