You can use the Admin API to bulk delete all of your Cloudinary uploaded resources in batches of 1000 resources per call.
For example in PHP:
You can delete only a certain type of resources, for example - Facebook fetched profile images:
$api->delete_all_resources(array("type" => "facebook"));
When there are still more resources to go through, the
next_cursor value is returned as part of the response. You can then specify this value as the
next_cursor parameter of the following call. This way you can go through the full lists of your resources.
For more information, see: http://support.cloudinary.com/hc/en-us/articles/205714121-How-do-I-browse-through-all-resources-in-my-account-using-the-API-
Note that the Admin API is rate limited.
UPDATE: A new UI bulk delete is now available! In addition to bulk deletes via the API, you can execute a bulk deletion jobs by going to your Account's Settings page and click the Bulk delete button from the Support activities section -