Celebrities have now become walking and talking billboards with many of them endorsing several brands at one time. While some ad makers feel stars are often used as substitutes for lack of fresh ideas and that one person selling multiple products can confuse consumers, many feel stars, if used well, can up the creativity of commercials.

"Clients who don't have great ideas for their brands ride on stars to deliver their brand message, " said Titus Upputuru, ex-senior creative director of Ogilvy & Mather.

But ad filmmaker-turned-director Dibaker Banerjee, who owns Freshwater Films, has a different take.

"I don't feel that a celebrity is a substitute of ideas. A good idea and a strong creative are the requisite of any ad, and if an ad film doesn't possess that, then a celebrity cannot create it, " Banerjee told.

Said ad guru Prahlad Kakkar: "Celebrities are not substitutes for ideas. In fact, the bigger the celebrity, the bigger the idea should be for the product to get noticed."

According to Bhavna Kher, creative supervisor at Ogilvy & Mather, most big stars are consulted before the shoot of a commercial.

"Their inputs are valued and sometimes even implemented. Aamir (Khan) and Shah Rukh (Khan) are known for being totally involved in their commercials, " said Bhavna.

The endorsements are no doubt rewarding for the superstars. While Amitabh Bachchan earns Rs.1.2 billion per year by doing commercials, daughter-in-law Aishwarya Rai takes home over Rs.1 billion. Hrithik Roshan too earns over Rs.1 billion through endorsements.

While a celeb's job is to do what the script says, the creative team has to ensure that they fully utilise the stars' popularity to make the commercial profitable.

"The most important factor, which is borne in mind while churning out an ad with a celebrity is that the celebrity shouldn't be bigger than the idea of the ad. The product for which the ad is being made should be visible and not lost in the ad, " said Kakkar.

After almost exhausting the one celebrity formula in ads, making commercials has become a star-studded affair now with multi-starrer advertising.

For instance, the voice SMS commercial for Airtel featured Shah Rukh, Saif Ali Khan and Kareena Kapoor. A Ponds campaign had Neha Dhupia, Priyanka Chopra and Saif Ali Khan.

The biggest of them all was the launch ad of Airtel DTH where seven stars - R. Madhavan, Vidya Balan, Zaheer Khan, Gautam Gambhir, Kareena Kapoor, Saif Ali Khan and A.R. Rahman - came together.

But too many celebs in one ad are not as confusing as one star endorsing too many products.

Ace cricketer Sachin Tendulkar endorses myriad brands like Pepsi, Boost, MRF, Fiat Palio, Colgate Total, Britannia, Visa, Airtel, Royal Bank of Scotland and many more.

Shah Rukh Khan sips Pepsi, zooms around in a Santro, sports a Tag Heur and then sells Nokia phones and Dish TV too. Aamir Khan competes with Shah Rukh by promoting Coca-Cola, the Toyota Innova car, watches by Titan, Samsung phones and Tata Sky.

Similarly, Preity Zinta is seen in the ads of Rexona Deo, Godrej, BSNL telecom and the new airline Go Air.

"In an age when each celebrity is lending his/her name to varied brands, it is very important for the advertiser to completely change the appeal of the celebrity so that the ad doesn't lose its importance. If your creative appeal is not strong, then your ad will anyway fall in the clutter, " said Banerjee.

But linking a product with a celebrity is not always a safe bet. It can give opposite results if the star gets into controversies.

"If a celebrity endorsing a particular brand lands into a controversy, it's important to distance the brand from that person so that it doesn't show the product in bad light, " said Kakkar.

Said Bhavna of Ogilvy & Mather: "Our audiences are intelligent, but also vulnerable and sensitive. Ideally, the celebrity should be taken off the brand for some time until the memory of the controversy subsides."

Banerjee, however, felt that a firm usually ropes in only personalities who have a clean image in the minds of people.

"Small controversies do not have a great impact and are avoidable, " he said.