This offer arrived in my inbox:
Earn 500 MB for every friend who installs the Dropbox desktop app—and your friend will get 500 MB too. They can sign up for any plan and you get your bonus space the minute they download the app.
If you’d like to be that friend, and only if this offer is of any value to you, maybe just as extra security to backup some particularly valuable files using a new free account, sign up at https://www.dropbox.com/referrals/AACscMD2gOa9FFAVXkGnTvWuo_yGZGd7YcU?src=global9
In case you’re not familiar with Dropbox, take a look at this 15 minute video.