YouTube has a major challenge with their adoption of HTML5, they want to leverage the new format and capabilities, but they don't want to make it easy to download videos. This is going to be one of the biggest challenges youtube faces until they realize that allowing users to download videos will not reduce their market position or decrease ad revenue.

Originally with the flash version, downloading youtube videos was as easy as copying the unstreamed files from /tmp/ assuming you are using linux. With the introduction of HTML5 videos (both .h264 and webm videos) they made it a little bit harder, because HTML5 videos were not stored in adobe's cache, but in your browsers further obfuscated cache. This was overcome by disabling a content blocking box that they put over the video.

Round 2 of Downloading YouTube Videos

Now it seems they have updated the site again, and some additional sleuthing was required to see what they were doing. They are now using javascript to capture and ignore the right click event when you click on the video. I have expanded my bookmarklet to fix this issue as well. I left the original unblock code in there just in case they try multiple techniques. Drag this bookmarklet to your bookmark bar. This bookmarklet unhooks the context menu capturing event, and removes a blocker box if one is found.