Maybe Taylor Swift can write a song about this!

Last night's Vanity Fair after-party at Sunset Tower in Hollywood was packed to the gills with A-listers: Madonna and daughter Lourdes, Gwyneth Paltrow, Cameron Diaz, Scarlett Johansson, Colin Firth, Amanda Seyfried, Gerard Butler, Sandra Bullock and many others.

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Also among the revelers: country singer Swift, 21, her ex Jake Gyllenhaal, and his ex Reese Witherspoon!

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No word yet on whether any of the former lovers endured any awkward run-ins at Sunset Tower. Gyllenhaal, who split with Swift via phone just before New Year's, brought his Oscar date (an unidentified young, curly-haired brunette) and chatted with Vera Farmiga, 50 Cent and other stars. See more photos from the Vanity Fair Oscars party.

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Clad in Armani Prive and $1 million worth of Neil Lane jewels, Witherspoon, 35, showed up at the bash with her fiance, CAA agent Jim Toth. She and Gyllenhaal, 30, split in late 2009 after a year and a half together.

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