Dropbox is down -- break out the FTP client. According to readers and Twitter, the service has been out of action for just over half an hour and while you might see the green tick of syncing joy on your PC, we were still unable to upload any new files through both the internet and desktop iteration -- in fact the web interface is completely down. We're not sure if this is a server issue or perhaps a delicious new feature with teething issues, but we've reached out to Dropbox and will update when we hear back.
Update: Looks like you can return to your regularly-scheduled uploading. Still no word on what caused the incident yet.
[Thanks to everyone who sent this in]