Not really "hacked" if you read the article properly.
One of their employee Dropbox accounts was compromised via a stolen password (which, as it happens, contained sensitive info). The only result was spam (potentially of the social engineering type) to a selection of users. In addition, some users had their accounts accessed due to using the same password as on other sites, which had been hacked in the past, ie. poor user security.
That said, I'm more than happy for them to increase their security, given the convenience of using Dropbox for sharing useful things like KyPass files between devices.