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Shouldn’t single actresses know by now that giant diamonds worn on a particular finger shouldn't be flaunted in public? Cameron Diaz was photographed sporting an ostentatious sparkler yesterday in Santa Monica, suspiciously displaying the gory piece on her engagement ring-reserved finger in a very blatant manner. But considering she’s just barely started dating former cokehead/Jennifer Aniston ex Paul Sculfor, and has been linked to half a dozen other canoodling partners in the past few months, we’re not jumping on the “Diaz Engaged!” bandwagon quite yet. The notoriously anti-paparazzi actress might have just wanted to fuck with her camera-flashing enemies. Still, whenever a star makes the decision to debut a big ol’ gem there, it’s proven tough to gage those inevitable engagement rumors’ validity. We looked back at celebrity diamond-spotting of the past, from the most firm denials that led to splashy weddings, to the sure things that turned out to be false alarms, after the jump.

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The Fake-Outs: Mid-2007, before Britney was deemed an American Tragedy, she was on her way by tragically dating the poor man's David Blaine, Criss Angel. And photos of her blonde-weaved sunglasses-at-night self wearing a sparkler set the Britney-hungry gossips ablaze, only to disappoint us when no marriage plans surfaced. Another Bimbo Summit alum, Lindsay Lohan, was rumored to be on the soberific path towards married life with then-beau Harry Morton in 2006 after showing up to a premiere purposely placing a ring-adorned hand on her hip. But we all know how that union turned out. And the most recent and admittedly exciting engagement rumors were sparked after photographs of Kate Hudson wearing a real-life wedding band surfaced just as gossip started spreading that she and Owen Wilson were back on. But a major "D'oh!" was heard loud and clear after realizing Kate was filming this flick called Bride Wars and merely in character.

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The Real Things: Beyonce Knowles started wearing massive diamonds on all her fingers ever since she could afford them, but the one she wore this January while sitting next to Jay-Z at a concert ended up being the engagement variety after all. And just days after being photographed candidly in her car with a new rock, Jessica Alba confirmed her engagement to the confusing man of mystery that is Cash Warren. As for Mariah Carey, poor girl sparked engagement rumors by publicly showing off her ring from Nick Cannon, only to learn soon after the actual wedding that it was recycled. Oops.

[Photo Credits: Fametastic, Showbiz Spy, Female First, Babble, Stupid Celebrities, Hollyscoop, Daily Mail]