Hewitt, who landed the number one spot on the list, underwent three hair changes this year: after cutting her hair into a shoulder-length 'do with full, blunt bangs in September, she lengthened her locks with 12-inch hair extensions a month later. And just last week, the Can't Hardly Wait actress made the switch from a rich brunette color to a deep red hue.
Watson may have chopped off her hair into a cool pixie cut in 2010, but the Harry Potter star's chic crop still managed to help her nab the number 2 spot on Yahoo!'s list.
The rest includes Kate Gosselin, Olivia Wilde, Justin Bieber (who cut his hair in February), Nicole "Snooki" Polizzi (who's rocked extensions in every color under the rainbow), Ashlee Simpson (who went platinum blonde in January), Reese Witherspoon and Rumer Willis (ranked in order listed).