используйте гем 'youtube_it'.Затем в контроллере или помощнике ...
client = YouTubeIt::Client.new(:dev_key => "dev_key_supplied_by_youtube_after_you_register_for_their_api")
videos = client.videos_by(:user => "some persons youtube username)
count = videos.total_result_count
Затем в поле зрения
<%= "So and so has <%= count %> videos on youtube" %>