The Dropbox team has been working hard on Webhooks for some time now, it looks like this is a much-needed tool for developers.

For example, a little under a year ago I released a mobile writing app that synced using the Dropbox Sync API. Right out of the gate there were problems syncing large documents, specifically due to slow mobile connections. The webhooks functionality (while I haven't launched a version of the app that implements this) allows me to check for changes quickly on a server before syncing files on the user's device.

Kudos to the team on adding a much-needed feature to the Dropbox functionality.