YouTube has announced that their search are now a part of Google Trends. To try YouTube Trends search, visit Google Trends, enter a search keyword, on the search result page select “YouTube” under the “limit to” option on the left. That will provide you with the current search trend of the keyword on YouTube search.
YouTube informs: Search query interest can often provide a more detailed picture into the life of a trend or topic. For example checkout the increase in interest for Harlem Shake on YouTube.
For more details join in on the discussion at Google+.YouTube Searches Now Part of Google Trends!,