What goes up must come down, right?

Not necessarily. Netflix (NASDAQ:NFLX), which was the best-performing stock in 2013 -- and is beating the market again so far this year -- just attracted a $500-a-share price target from RBC Capital analyst Mark Mahaney

In the video below, Fool contributor Demitrios Kalogeropoulos reviews Mahaney's reasoning for the upgrade, noting that he has been a longtime bull on Netflix's shares. For example, Mahaney upgraded the stock back in September 2013, when shares were trading for $300 a piece, after RBC's survey on Internet video trends came back with unusually strong results for Netflix.

This week's upgrade is for basically the same reasons, Demitrios notes. RBC's latest survey found that Netflix just surpassed YouTube for the first time as the most popular destination for online video consumption. Netflix also hit another milestone recently, RBC estimates, as the streamer's user satisfaction levels are at a new record high.

If true, those trends would be great news for Netflix's business, as they suggest that the company is having more success in attracting new customers and in retaining the ones it already has, likely thanks to an improving user interface and growing content library. That strong base of growth in the U.S., plus an ambitious expansion into Europe later this year, could justify the roughly 15% increase in shares that would put the stock above $500, Demitrios argues. Still, given Netflix's huge run, investors should tread carefully with this stock.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.