Hulu, once heralded as a YouTube killer, turns one year old this week, and while the video streaming site is not yet profitable, it has found immense popularity with marketers and, perhaps more importantly, with viewers.

Since it debuted in beta testing a year ago, Hulu has grown from 10 sponsors to 100. But the biggest news is that it has found an advertising model that doesn't deter viewers. Hulu streams full-length movies and television episodes with only one ad shown during breaks, and 76 percent of viewers said this was the right amount of ads to justify the free content.

A joint venture between NBC Universal and News Corp., Hulu is now the sixth most popular video brand online, according to The New York Times. In September, 6.3 million unique visitors streamed 142 million videos on the website, according to Nielsen.

YouTube, far and away the leader in online video streaming, has struggled to find a monetization model and recently experimented with pre-roll advertisements and a click-to-buy model.

At the same time, a recent surge in traffic actually has Hulu facing a shortage of video advertising. Two "Saturday Night Live" skits featuring Tina Fey as Sarah Palin have been viewed a combined 21.3 million times since they debuted in September. Hulu traffic has also been buoyed by fall TV premieres, one of which, "30 Rock," debuted on Hulu a week before premiering on TV.