Twitter is (in a way) because Old Spice has coordinated this with a promoted trending topic and a promoted tweet. YouTube is (in a way) as well since Old Spice

Twitter is (in a way) because Old Spice has coordinated this with a promoted trending topic and a promoted tweet. YouTube is (in a way) as well since Old Spice is probably paying for their channel. Reddit, maybe, if Old Spice became a Gold Member.