Youtube has finally taken orkut seriously and has provided an Orkut share option in its share list. All you need to do is click on Orkut in Share option under any youtube video you want to save as your fav in Orkut. You will be redirected to Orkut.com where you have to confirm if you want that video as your favorite.
Not so smooth, it would have been much better if we could connect our account to youtube account and a single click would have done the purpose. But something is better than nothing