"Everything that Lindsay Lohan has done has been pretty unfortunate," says Adam Hanft, founder of the branding firm Hanft Projects. "When you're famous for being famous, it's more difficult to extend that ephemeral celebrity value you need for a more substantive brand value."
Successful celebrity lines typically have one thing in common, experts say: a clear correlation between the brand's attributes and the celebrity's values.
"As a celebrity you have to understand why people buy you, and what makes people come back to you again and again," says Andy Bateman, CEO of Interbrand, one of the world's largest branding agencies.
Justin Timberlake's fashion line William Rast, for example, is considered a hit because the singer "kept it simple" and "jumped on the denim bandwagon when it was extremely popular," says Marissa Rizzutto, a fashion designer who has made jewelry for pop star Fergie.
Experts say that Timberlake had already built a lot of good will among consumers as a credible musician and stylish dresser, so when he decided to launch a fashion line, he had some "brand equity" to cash in.
Another example is Sean Combs (aka P. Diddy), who started a joint venture with Ciroc Vodka. It works, says Bateman, because both the drink and Combs conjure up images of "a premium lifestyle."
"It wouldn't make any sense for him to do Budweiser or Coca-Cola," says Bateman.
That doesn't mean celebrities should only brand the kind of things they personally would use. Their daily budget, after all, often looks more like an average worker's monthly income. That's why many celebrities follow a strategy that combines the best of two worlds: bringing their luxury tastes down to a price that mass audiences can afford.
This formula, which Bateman dubs "champagne at beer prices" has led to an explosion of celebrity branded products in recent years.
Fashion is the biggest market. Reality star Kim Kardashian has designed an entire line of slinky dresses for Bebe. Kanye West has designed an eponymous line of sneakers for Louis Vuitton. J Lo tried her hand at tight jeans for curvy women.
"Nowadays, it seems like every celebrity wants to design a line of clothing. Some are hits but most are misses, mainly because they know nothing about the fashion industry," says Rizzutto.
It's also impossible to walk into a perfume shop without stumbling over another celebrity fragrance. Just think of "Intimately Beckham" by former Spice Girl Victora Beckham and "Usher" for Him and Her.
Perfumes can be tricky, however, since fragrance is considered a very personal product. Consumers don't want to compromise their personality too much by taking on someone else's scent, says Julia Beardwood, founder of Beardwood & Company, who has worked with everyone from the model Iman to Calvin Klein.
Male fragrances, especially, can end up looking very tacky, she says, since men tend to be more conservative in their grooming choices. Beardwood says scents from Antonio Banderas, Donald Trump and Prince's 3121 are branding "don'ts."
"Many men like Prince but I don't know if they want to smell like him," she says.