MoffettNathanson analyst Michael Nathanson downgraded Roku to Sell from Neutral with a price target of $220, down from $330. The stock closed Tuesday up $1.67 to $276.46. “Simply put, we think our and the Street’s long-term revenue and earnings estimates are just too damn high,” Nathanson tells investors in a research note. Roku will need to monetize an “absurdly high portion of long-tail” ad-based video on demand impressions to come even close to Street estimates, says the analyst. Nathanson believes this will be a challenge given rising competition and sees signs of slowing revenue growth at Roku.