For employers, the temptation to check up on a candidate on their social networking websites is often too hard to resist â€“ even if the information might prove misleading, or worse, give grounds for a discrimination claim.
The use by headhunters, recruitment agencies and human resources departments of websites such as LinkedIn has become ubiquitous and, some say, invaluable in allowing them to view details of a candidate's professional background, experience and contacts.
But when it comes to viewing a Facebook page or a Twitter feed, the line between the personal and professional can be blurred. In just a few clicks and seconds, employment discrimination laws can be flouted if someone decides they do not like the look of a candidate and makes a snap and superficial judgment against them.
Professionals need to be more aware than ever of their "digital reputation" across a range of internet sites in the knowledge that ultimately, it can be as hard to prove discrimination in the virtual world as it is in real life.
"I know recruitment agents use LinkedIn extensively as part of an initial search but it can be intrusive if they look at, say, Facebook because members often use it in a very different way to socialise," says David Robertson Mitchell, director of dna-rB Ltd, which provides personal branding coaching and advice.
"Recruiters could fall foul of the law if they make decisions based on someone's private life but the onus is on the prospective employee to protect themselves from information that is in the public domain."
Professionals should have long ago realised that, although it might be unfair, pictures of them behaving badly â€“ or oddly â€“ even on a friend's Facebook page could impede their chances of securing their dream job in top management.
Mr Robertson Mitchell tells of one client who managed their online presence only passively. He had a Twitter account but did not look at it for nine months during which it was hacked and filled with dating tips, providing a most unprofessional impression to any headhunter. "The client said Twitter was part of his private life but I was able to find it and so could anyone else, so you need to be aware of what's out there," Mr Mitchell says.
Broadly, people deal with privacy issues in their work and private lives in four ways, says Nancy Rothbard, associate professor of management at the Wharton School of the University of Pennsylvania.
Some people use a "content approach" and accept all friend requests but are careful not to post any revealing information and content. Others take an "audience approach" and vet their online friends carefully, rejecting those with whom they do not want to share their personal information.
Some people have a "hybrid strategy" and use privacy settings so that they share less sensitive information with certain friends and allow closer friends to see all their posts. The final group, often younger people, takes an "open approach" and shares all information, making no differentiation between online contacts.
"Young people aged 25 and under and who are more tech-savvy are more likely to have a belief in a transparent society and say, 'So you saw me partying, that's who I am; get used to it'," said Prof Rothbard. "But they can still have notions of hierarchy and have a sense of discomfort with being 'friends' with their boss as they do with their mums, so I'm not so sure that things are changing that fast."
She worries about the "decontextualisation" of information available about individuals on the internet.
"Social networking sites have given people a new window into people's private lives and it's very tempting to look in order to make an assessment about candidates. But there are lots of questions about vulnerability and trustworthiness," she says.
"Even people who are very careful to edit content about themselves in order to enhance and present their best 'self' do slip up. In addition, one can tell a lot about people if they self-edit and take care about how they appear, which might be a plus in some employers' minds."
Some sectors are perceived as being more worried than others about the reputational risk posed by employee posts â€“ for example, in banking or law compared with a more relaxed approach in high-tech start-ups or other creative industries.
But professionals need to think about the whole span of their careers and not just their 20s or 30s. "In the last 15 or 20 years, there's been a shift and there are very few jobs for life so people need to think about success over 50 years as they move from job to job," says Mr Robertson Mitchell.
In the US, the legal framework concerning what prospective employers are allowed to do when checking a candidate's online background varies from state to state and is vulnerable to legal challenge. For candidates, possessing two Facebook pages, one for personal and one for professional use, might not help because, although unlikely, they could be open to potential charges of personal misrepresentation in some states.
Stuart Soffer, director of patent strategy and analysis at a IPriori, an intellectual property consulting firm, and a non-resident fellow at Stanford Law School's Centre for Internet and Society, says he has not heard of any employer asking candidates for their Facebook passwords although this issue has been discussed in the US media recently.
"But there is definitely a 'biz app' waiting to be created that could preview and critique websites for an individual, telling them what's good and bad on their Facebook page, for example, just as some companies already do for people's rÃ©sumÃ©s," he says.
A recent survey by the US jobs site CareerBuilder of more than 2,000 hiring managers and human resource professionals found that 37 per cent said they researched job candidates on social networking sites.
In the UK, recruiters say they often use sites such as LinkedIn but not those such as Facebook, which can carry content akin to gossip.
"I think LinkedIn has increased the frequency with which employers are able to make direct contact with candidates," says David Mitchell, human resources director for Aquilaheywood, a life and pensions administration software company.
"From the perspective of both the job seeker and the employer, it's important to have guidelines in place when conducting social networking research. By introducing a standard protocol that applies to all candidates there is less potential for discrimination issues to arise."