By Rory Cellan-Jones
Technology correspondent, BBC News
Facebook's 40 million users should not worry that personal details will be available to anyone searching the net.
The firm's first overseas office will be located in London
That was the message from executives at the social network who are in London to set up their first overseas office.
Facebook's plan to make user profiles available to search engines has provoked anxiety amongst some users and attacks from privacy campaigners.
But the firm's head of privacy said that the idea that personal data would be exposed was "completely wrong".
"The only data that will be available is your profile picture and your name - and then only if you agree that your profile should be searchable," said Chris Kelly.
Facebook announced the move to open users' profiles to search engines such as Google in early September.
In addition, the firm has added a public search function to its site which will initially allow anyone, even if they are not registered with the site, to search for a specific person
At the time of the announcement, Om Malik, an influential blogger, wrote: "This is yet another small step in the overall erosion of personal privacy."
"We are slowly leaving digital litter all over the web, and some day it is going to cause problems."
But Mr Kelly insisted that the company offered new users plenty of advice on protecting their profiles from unwanted visitors, and 20% had changed their privacy settings.
But he said people had to use common sense: "You would not walk down the street with your mobile phone number written on your forehead, and you shouldn't do that on Facebook either."
Facebook had been working with the Home Office in Britain on child protection and privacy issues, he added.
Later this month Facebook will open an office in London's Soho, the first overseas operation for a firm whose 300 staff are mostly based in Palo Alto, California.
With 5.2 million users active in the last month, the UK is Facebook's fastest growing market.
Other sites are more popular than Facebook in the UK
It is attracting rather older users than in the USA, where it started as a network for college students. 54% of UK users are over 25, and the over-35s are the fast growing age group.
"The service is now incredibly diverse," said Chamath Palihapitiya, Facebook's Vice-President for Product Marketing.
"75% of our users are outside college - a significant majority are in the 30 plus age demographic. It's a social utility that has become very pervasive and useful for a wide variety of people."
Mr Palihapitiya also revealed that Facebook now aimed to have 60 million active users worldwide by the end of this year, having already passed its original 2007 target of 40 million users.
This year's rapid expansion has been partly fuelled by the opening up of Facebook to outside software developers in May.
So far they have created 3000 applications, and 80,000 developers around the world are working on new ones, in effect transforming the social network into an operating system for no payment.
Chamath Palihapitiya points to the two young Indian developers who have produced a Facebook scrabble game that is now amongst the most popular applications: "You have Fortune 500 companies doing this and you've got two kids in India. It's very empowering for the whole community."
But the big question for those developers and for the Facebook management is how to introduce more sophisticated advertising to the site, to generate more revenue without annoying users.
The Facebook executives are vague about their plans but it is clear they want to give advertisers more opportunities to target individuals according to their interests.
So someone who lists Forty year Old Virgin as one of their favourite films could find a trailer for Knocked Up popping up on their page.
While Facebook is attracting all the attention at the moment, it is worth remembering that it is still not the most popular social network in Britain.
That is either MySpace or Bebo, according to whether you believe Nielsen netRatings or Comscore.
But Nielsen is predicting that Facebook will overtake MySpace in the UK this month.
Social networking is now a very big business and the UK market is a key battleground.