Update: The group originally claiming credit for the database breach has since acknowledged they had only performed a distributed denial of service attack. It seems the group simply used the maintenance-related Dropbox outage as an opportunity to troll the Internet. You win this round, @1775Sec.
Update 2: The Dropbox website is back up.
Update 3 - 1/11/14: Dropbox's status page shows that maintenance is still ongoing. Users continue to report trouble using some services.
Earlier this evening, Dropbox began experiencing service outages with hackers taking credit on Twitter a short while later. Dropbox issued a statement indicating that the outage was the result of an issue that arose from recent maintenance.
We have identified the cause, which was the result of an issue that arose during routine internal maintenance, and are working to fix this as soon as possible.
While the group of malicious hackers, @1775Sec, initially stated they would give Dropbox time to fix the issue before deciding to leak any compromised information, the group has since posted partial leak of supposed Dropbox user data on Pastebin.
The partial data set appears to contain first names, last names, email addresses, and possible ID numbers for some 100+ users. So far there are no indications that any user-stored files have been compromised, or any confirmation from Dropbox that there was a breach.
While some have interpreted Dropbox's statement to mean the downtime was a result of internal maintenance and a denial of a security breach, it's possible that whatever vulnerability may have allowed the breach was introduced or left open as a result of the recent maintenance.