|Archiving status||Not saved yet|
Several free FLV downloaders and video-to-URL converters exist on the web.
AT rescue projects usually use youtube-dl.
YouTube annotations (speech bubbles and notes) are available as XML
To transform this XML to SRT, use ann2srt
Recomended way to archive Youtube videos
First, download the video/playlist/channel/user using youtube-dl:
youtube-dl --title --continue --retries 4 --write-info-json --write-description --write-thumbnail --write-annotations --all-subs --ignore-errors --merge-output-format mkv -f bestvideo+bestaudio URL
This can be simplified by running the script by emijrp and others, which also handles upload.
You need a recent (2014) ffmpeg or avconv for the bestvideo+bestaudio muxing to work. On Windows, you also need to run youtube-dl with Python 3.3/3.4 instead of Python 2.7, otherwise non-ASCII filenames will fail to mux.
The --merge-output-format mkv flag is used for cases where the highest quality video+audio is webm+m4a. You can use -f bestvideo[ext=mp4]+bestaudio[ext=m4a] instead if mp4 files are a requirement, although you might not get the highest quality.
Then, upload it to https://archive.org/upload/ Make sure to upload not only the video itself (.mp4 or .mkv files), but also the metadata files created along with it (.info.json, .jpg, .annotations.xml and .description).
Little is known about its database, but according to data from 2006, it was 45TB and doubling every 4 months. At this rate it would be 660 Petabytes (Oct 2014) by now.
According to Leo Leung's calculations based on available information, an often updated Google spreadsheet estimates that in early 2015 YouTube's content reached 500 petabytes in size.
FYI, all of Google Video was about 45TB, and the Archive Team's biggest project, MobileMe was 200TB. The Internet Archive's total capacity is 50PB as of August 2014. So let's hope YouTube stays healthy, because the Archive Team may have finally met its match.
Will be living off Google for a long time if nothing changes.