Videos by a self-styled Obama Girl, a fan's tearful defense of Britney Spears and an attack by a herd of buffaloes on a pride of lions, were among the most popular clips on YouTube.com in 2007.

But the videos were not just popular because of the millions of times they were seen on the YouTube.com Web site, which allows users to post their homemade videos. The rankings, released by YouTube on Thursday, took into account the most shared, most discussed, top rated and general popularity of clips to determine which ones people were thinking and talking about most.

Among the year's favorites were the Obama Girl video, created by Barely Political, featuring an attractive young singer professing her love for Democratic presidential candidate Sen. Barack Obama. It has been viewed more than 4 million times and many more times on television after being featured on news and talk shows.

While it was clear Barely Political was producing political satire in the name of entertainment, Internet surfers might initially have been less certain what Chris Crocker was trying to do in his Leave Britney Alone clip in September.

The clip is a close-up of Crocker breaking down in tears as he berates the media and paparazzi for hounding pop singer Spears as she lurched from one tabloid scandal to another.

YouTube said the melodramatic two-minute clip made Crocker an instant YouTube star, has been watched more than 14 million times and is the fourth most-commented-on video in YouTube's history.

In terms of sheer viewer numbers it was an unlikely combination of amateur production values, patience and timing that made an eight-minute video titled Battle at Kruger so compelling it has been watched more than 21 million times on YouTube.

The video captured the battle between a herd of water buffaloes, a pride of lions and a crocodile over a young calf.

The clip, filmed by Jason Schlosberg on safari in South Africa's Kruger National Park, has been featured on ABC News and Time magazine. Schlosberg has a documentary coming on the National Geographic Channel next spring based around his original film.

Other popular videos included performances by up and coming singers in their bedrooms, including Esmee Denters from the Netherlands, singing Justin Timberlake's What Goes Around or Tay Zonday singing an original composition Chocolate Rain.

A piano playing cat named Nora and otters holding hands also were among the favorites on YouTube, which is owned by search engine company Google Inc.

(Editing by Michelle Nichols and Bill Trott)

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