Many of the boldfaced names at Michael Jackson's Staples Center memorial hardly knew the singer, or hadn't spoken to him in years.

Brooke Shields, who broke down in tears as she recalled her "true friend," hadn't seen him in 18 years -- since Liz Taylor's 1991 wedding.(A memory she said was one of her favorite.) John Mayer -- who performed "Human Nature" -- admitted he'd never met Jackson. Neither did Jennifer Hudson, who performed "Will You Be There."

Mariah Carey worked with Jackson on his 2001 charity single "What More Can I Give?" but wasn't close with the singer, a source tells She also had a hit with the Jackson 5 classic "I'll Be There." Usher, who sobbed and touched Jackson's coffin while singing "Gone Too Soon," performed with Jackson at his 2001 celebration concert at New York City's Madison Square Garden. But "their contact was minimal," the source tells Us.

Corey Feldman -- who sported a Jackson look from his Dangerous era -- befriended the singer in the 1980s as a teen, but they drifted apart and didn't speak for several years before his death. Many of Jackson's actual friends were not present. Diana Ross -- who was named as a backup guardian to Jackson's three children after his mom, Katherine -- issued a statement instead of attending.

Arnold Klein, Jackson's longtime dermatologist and biological father to his two oldest children, was also noticeably absent. Both ex wives Debbie Rowe and Lisa Marie Presley also stayed home. Taylor said she was asked to speak but Tweeted she couldn't "be a part of the public whoopla" or guarantee "that I would be coherent to say a word." Producer Quincy Jones, who helped launch Jackson's career, said he couldn't "handle it" and instead went to a charity event in Europe.

Macaulay Culkin -- who became friends with Jackson as a kid, and even defended him at his molestation trial (he was acquitted) -- skipped it. Even Jesse Jackson, who counseled the singer during his trial, was not present to speak. A source tells Us Joe Jackson hates him, and made sure Al Sharpton delivered a speech instead.