Jackson, who had been expected to enjoy a clean sweep, ended up with four awards. He and Swift went head-to-head in the Artist of the Year race, the ceremony's final prize.
"Music has never been ultimately about competition," Swift said, after winning the artist of the year prize. She said it was an "unimaginable honor" to be cited in the same category as Jackson, and thanked the Jackson family.
Swift -- who accepted her award live via satellite from backstage at London's Wembley Arena, where she will perform a concert on Monday -- was also named favorite female artist in the pop/rock and country categories, and favorite adult-contemporary artist. Her 2008 album "Fearless," the best-selling release in the United States this year, was named favorite country album.
But it was the performances that really turned heads during the three-hour ceremony, which drew in more than 14 million viewers. "American Idol" runner-up Adam Lambert shocked the crowd with a racy performance of his new single "For Your Entertainment," during which he simulated oral sex with one male dancer, kissed another male keyboard player and grabbed the crotch of a female dancer.
Jennifer Lopez, meanwhile, landed on her bottom after jumping off the arched back of one of her dancers during her performance of her new song "Louboutins."
The AMAs also boasted memorable performances from Janet Jackson, who opened a show with a medley of some of her biggest hits, Lady Gaga, Carrie Underwood, Green Day and Whitney Houston, who recieved thunderous applause for her emotional rendition of "I Didn't Know My Own Strength."
Jackson was named favorite male artist in the pop/rock and soul/R&B categories, while his 2003 hits collection "Number Ones" was named favorite album in both those categories. The album is the No. 2 seller this year in the United States.
His brother Jermaine, accompanied by sons Jeremy, Jaafar and Jermajesty, accepted on his behalf. At one point, he thanked Allah "for blessing my entire family."
Eminem, making a rare awards-show appearance in the wake of his four nominations, went home empty-handed. Lady Gaga, rock band Kings of Leon and jailed rapper T.I., who earned three nominations each, were also snubbed.
The Black Eyed Peas were named favorite group in both the pop/rock and soul/R&B categories. Jay-Z won favorite male artist and favorite album in the rap/hip-hop categories. His wife Beyonce, who was performing a show in Dublin, was named favorite female artist in the soul/R&B category. Punk rock trio Green Day won the favorite alternative artist. Rascal Flatts won favorite country group for the fourth year in a row.
Nominees are determined by radio airplay and retail sales, while members of the public determine the winners through online voting. That's why Jackson got so many nominations, even though he didn't release any new material.
(additional reporting by M. Tye Comer for Billboard)
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