Notably, some content creators hosted their content on their own websites, such as Joel Veitch's site for his band Rather Good, which hosted quirky Flash videos for the band's songs; the most popular was "We Like the Moon", whose viral popularity on the internet prompted Quiznos to parody the song for a commercial. The most famous self-hosted home of viral videos is perhaps Homestar Runner, launched in 2000 and still running. The introduction of social media such as Facebook and Twitter has created even more avenues for videos to go viral. More recently, there has been a surge in viral videos on video sharing sites such as YouTube, partially because of the availability of affordable digital cameras. Beginning in December 2015, YouTube introduced a "trending" tab to alert users to viral videos using an algorithm based on comments, views, "external references", and even location. The feature reportedly does not use viewing history to serve up related content, and the content may be curated by YouTube. Qualification There are several ways to gauge whether a video has "gone viral". The statistic perhaps most mentioned is number of views, and as sharing has become easier, the threshold requirement of sheer number of views has increased. YouTube personality Kevin Nalty (known as Nalts) recalls on his blog: "A few years ago, a video could be considered 'viral' if it hit a million views", but says as of 2011, only "if it gets more than 5 million views in a 3–7-day period" can it be considered "viral". To compare, 2004's Numa Numa received two million hits on Newgrounds in its first three months (a figure explained in a 2015 article as "a staggering number for the time"). Nalts also posits three other considerations: buzz, parody, and longevity, which are more complex ways of judging a viral video's views. Buzz addresses the heart of the issue; the more a video is shared, the more discussion the video creates both online and offline. What he emphasizes is notable is that the more buzz a video gets, the more views it gets. A study on viral videos by Carnegie Mellon University found that the popularity of the uploader affected whether a video would become viral, and having the video shared by a popular source such as a celebrity or a news channel also increases buzz. It is also part of the algorithm YouTube uses to predict popular