By Rebecca Morelle
Science reporter, BBC News
For the nosy among us, it is the ultimate dream: having access to information about anyone, anywhere at the tip of your fingertips.
Some search engines are making it easier to find information about people
Search engines like Google, Ask.com or Yahoo have already gone some of the way to helping us do this.
Users can check out job applicants, dig up the background of potential partners and rediscover distant friends and relatives; the practice has become so prolific that the verb Google has even made its way into the Oxford English Dictionary.
But now several new sites are hoping to make waves in the personal search market.
Kevin Newcomb, news editor of Search Engine Watch, said: "People are always looking for people they know or, mostly, looking for information about themselves.
"Search engines like Google do a good job if you have a unique name - then they can find everything out about you, but if you have a common name, they don't really pay much attention to sorting that information out.
"These people search engines are trying to overcome this."
The niche search engines are making use of the information that is already out there about us on the web to cross reference details so they can index and build up searchable profiles.
Zoominfo.com, which came online in 2001, was one of the first sites to do this.
It began life as a subscription service where it gathered profile information from the web in response to requests from recruiters or salespeople, but in 2005 it added a public service, enabling free company and personal searches.
The search engines are trawling social networking sites
Russell Glass, the firm's vice president of products and marketing, said: "Users can come in and search for a person's name, and we essentially crawl somewhere between one billion and two billion pages to gather, organise and summarise a virtual resume.
"It provides a detailed and rich look at who a person is from a professional perspective."
The business-orientated directory contains more than 37 million personal profiles and 3.5 million companies profiles pulled from across the web.
Other search engines are aiming for a different market.
Some, like Wink.com, a US company that launched in 2006, are using the ever-growing swells of personal information found on social networking sites such as MySpace, Bebo and Friendster in addition to other web sources such as Wikipedia to create public profiles.
Michael Tanne, founder and CEO of Wink, said: "The Wink service is where people find people.
"It's targeted at anyone who is trying to find someone else online - old friends, new friends, dates, people they heard or read about, job searches, business leads, celebs etc."
Mr Tanne said users could search more than 200 million profiles but added that the company had ambitions to eventually index every person online.
Spock.com, which launched today, also trawls social networking sites. The search engine claims that it currently has more than 100 million people indexed, but like Wink it has big ambitions.
Its co-founder Jay Bhatti told the news agency AFP that he hoped it would eventually be able to provide a search result for everyone in the world.
Spock.com, like Zoominfo.com, Wink.com and other search engines such as ProfileLinker and Upscoop, allows users to take control of their profiles.
Rather than letting the fate of your profile be left down to what is written about you on the web, the sites allow users to amend, update or add new information about themselves.
But what if you do not like the idea of this kind of information being available at all?
Gus Hosein of Privacy International is worried about the sites.
He said: "Anything that makes personal information available to individuals is always at risk of being abused.
"Companies like this have to be very careful about who they are giving this information to. Now, of course, these search engines are making it widely available to everybody, which is a very dangerous step forward.
"If these companies operate under any European jurisdiction, or jurisdiction in the United Kingdom, there would be privacy laws, and technically, you could order these companies not to serve information about you."
Alan Chapell, an lawyer specialising in online privacy, added: "Given all of the information that is available on social networking sites, it was only a matter of time before someone began to compile that information.
"The caveat today is be careful what you post."
Search Engine Watch's Kevin Newcomb also cautioned that the niche search engines might not provide as lucrative an advertising revenue as the general search engines.
He said: "It's not a huge part of the market, and as far as the ads are concerned, it's not really much of a market at all. People don't want to buy adds on a person's name unless they are famous.
"Some will have demographic ads based on what the target audience is, but it is not as powerful as say, advertising an mp3 player next to an mp3 search."