Product Description
Here Is What You Didn't Know... NOW YOU CAN EXPOSE THEM. YouTube decided that they did not want to depreciate the power of tags as a ranking factor, so they simply started hiding the real tags on most videos.
If you're looking in the video page source and see the tags in the "keyword" section of the source, then I assure you that most of the time you aren't getting the actual tags used in that video.
I can also assure you that pretty much all of the software you have that pulls video tags for you is really doing nothing more than what you were doing manually. Checking in the keyword section for the tags that YouTube says it's using.