Since downloading youtube videos violates Youtube's terms of service, and in most cases can be viewed as copyright infringement upon the owner of the media being downloaded and as such be illegal we cannot really offer any suggestions.
Terms of Service - YouTube
Content is provided to you AS IS. You may access Content for your information and personal use solely as intended through the provided functionality of the Service and as permitted under these Terms of Service. You shall not download any Content unless you see a “download” or similar link displayed by YouTube on the Service for that Content. You shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content. YouTube and its licensors reserve all rights not expressly granted in and to the Service and the Content.
Apple Support Communities Use Agreement
Keep within the Law
- No material may be submitted that is intended to promote or commit an illegal act.
- Do not submit software or descriptions of processes that break or otherwise 'work around' digital rights management software or hardware. This includes conversations about 'ripping' DVDs or working around FairPlay software used on the iTunes Store.