Twitter gives an instant snapshot of the buzz around television shows, computer game launches and even new ads, but many media executives are simply too busy to tweet or engage with the microblogging service very much themselves.

Digital reluctance is particularly strong amongst old media leaders, who told this week's Reuters Global Media Summit they were uncomfortable with sharing personal information, especially in 140-character bursts.

Maurice Levy, chief executive of advertising group Publicis, said Twitter and its social networking sister Facebook were simply not for him.

I hate the idea that I would have to share things which are not for sharing or which are superficial, he said in Paris.

He said he kept tabs on social media in a professional capacity but he did not need to tweet to understand the importance of Twitter.

I understand how to wash dishes. I don't do it regularly, he said.

His rival Martin Sorrell, of WPP, who has never been reluctant to air his views on television, was not keen to join Twitter's 200 million users either.

I have enough to do answering your emails, he said. I'm 66 years old. I'm almost in the glue factory.

Arnaud Nourry of French publisher Hachette said the character limit was Twitter's drawback, and said he preferred Facebook.

I think communicating with text only with a very limited way of expression is not my style, he said.

The media executives were not keen to emulate musicians like Lady Gaga, sports stars like Shaquille O'Neal and Lance Armstrong or personalities such as Stephen Fry in using the medium to communicate with fans, or with investors.

Hearst Magazines president David Carey said he tweeted mostly corporate promotion and saved personal information for his friends and family.

For the rest of the world, I don't think they are interested in who I had dinner with ... or where am I going for vacation, he said.

Others used San Francisco-based Twitter to monitor news sources, particularly from key journalists.

I follow a whole bunch of journalists, but I don't tweet myself, said William Eccleshare, chief executive of outdoor ad company Clear Channel International.

Twitter is considered a leading initial public offering candidate for late 2012 or 2013, and it was worth about $8 billion on secondary markets in October.

It is ramping up efforts to generate more advertising revenues, which are expected to reach $145 million this year. Some observers had criticized its exclusive focus on building audience rather than sales in its early days.

The executives' comments show that Twitter may struggle to reach older decision-makers with ads, although younger guests at the summit were unsurprisingly far more engaged with Twitter.

Of course, said Claire Boonstra, co-founder of augmented reality company Layar, when asked whether she was on Twitter.

It's a great chance to connect, it's a great channel actually to share thoughts and opinions, and I also use it to stay up to date with friends of mine, she said. But it's for me more business than personal.

Targeted ads group Criteo's Gregory Gazagne said: I use LinkedIn and Facebook a lot more.

When I'm on Linkedin and I publish things they are automatically published on Twitter. But it takes me too much time to manage all the social networks.

David Norris, founder and chief executive of U.S. digital fingerprinting start-up BlueCava, said he got all of his news from Twitter, letting the people he follows do the hard work of digging out information instead of searching for it himself.

That's how I know AA just filed for bankruptcy, said Norris, who had just flown in to London from Los Angeles on American Airlines. They work for me. That's how it's supposed to be.

(Additional reporting by Lisa Richwine in New York, Leila Abboud in Paris and Georgina Prodhan in London; Editing by Hans-Juergen Peters)

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