Youtube is a good place for sharing Hive links - in descriptions of your own videos, for example, new or old. If you have a good video there, it will keep getting visitors for ages. Links in desc can lead people to Hive.
But I don't know how to measure this contribution because Youtube video content, unlike Tweets, collects views during a long time - weeks, months, years. But maybe the data of peakd's referral system can be used for POSH reward system in this case of another.
Just thinking out loud.