Anecdotes abound about professionals who have lost job opportunities over something they’ve posted online. New research confirms that employers are turning more frequently to the Internet to check out job candidates. A survey of 1,100-plus HR professionals by market research firm Cross-Tab found that 70% of recruiters have rejected a candidate for employment based simply on text, photos or videos they discovered about that person online.

“An applicant’s online reputation can be very important in the hiring process,” says Monique A. Honaman, CEO of ISHR Group, a human resources firm. “Essentially, this person will be representing your business, your brand. It behooves a company to be sure that the individual represents the company in the manner in which it wants to be known.”

Valarie Webster, senior vice president, The Flanders Group, an independent agency in Pittsford, New York, agrees. “With electronic media, information is available that doesn’t usually come up during interviews, background checks, or in references. It has to be taken into consideration with the rest of the information available to you so a complete picture can be drawn.”

Indeed, many of the HR professionals participating in Cross-Tab’s “Online Reputation in a Connected World” study say Web screening of candidates has become a formal requirement in the hiring process. And an overwhelming majority believe such screening and monitoring will weigh even more heavily in hiring decisions during the next five years.

“We would consider it a deal breaker if we found unprofessional or negative information about an applicant online,” says Karen K. Farris, CPCU, ARM, president & CEO, Roach Howard Smith & Barton, a Dallas, Texas-based independent agency.

Plus, most HR pros surveyed readily maintain they consider no online venue exempt from investigation. Indeed, in addition to typical social networks like Facebook and MySpace, these execs thought nothing of checking out online gaming sites, virtual worlds, as well as retail, auction and classified sites like Amazon.com, eBay and Craigslist before offering a position.

All told, an overwhelming majority of HR recruiters surveyed for the study (84%) believe poking into people’s personal lives online is perfectly acceptable. And even more (89%) believe investigating professional credentials online should be the norm.

Recruiters most comfortable with online screening also freely admit they’re able to unearth much more information about a person online than they’re able to—or even permitted to—via traditional job interviews and background checks.

While conventional job interviews would not include discussions of a candidate’s religious, political or other affiliations, financial situation, or medical history, much of this information is freely available online if you know where to look—and many recruiters are doing just that. The result: Some job applicants are being rejected based on their membership in certain groups online. Others are falling victim to comments made about them by friends, family or colleagues.

For human resource pros, perhaps the greatest power in online screening is anonymity. Essentially, both in-house and third-party staffers can pretty much stop anywhere they’d like on the Web, take a look around, and be gone without anyone being the wiser.

A recruiter, for example, may come across a photo of a job candidate at a political rally that’s been tagged with the person’s name, and consider that political affiliation as a factor in the hiring process—whether or not that individual happened to be attending that rally as an ardent supporter, or interested observer.

Currently, such photos are generally created and shared among friends on the social networks. But new online technology, like the free, Web-based Polar Rose (http://www.polarrose.com), now makes it possible to automatically match images of people with the names of those people.

The upshot is that in the not-too-distant future, it may become very easy for a complete stranger to take a picture of you anywhere, in any number of compromising or otherwise private situations, and instantly post that image to the Web—right along with your name and other identifying information.

“Today, facial recognition technology is standard in many new digital cameras, and applications like Polar Rose are soon going to be fused with the cameras and Internet connections on users’ phones,” says Mary Madden, a senior research specialist at Pew Internet, a nonprofit research group. “Google Goggles, a service that lets you use pictures taken with your mobile device to search the Web, doesn’t offer facial recognition for now, but the underlying capability is there.”

Not surprisingly, human resource pros like ISHR Group’s Honaman advise all job seekers to clear away the trash before they send out the first résumé and begin building an online image that gleams.

Clearly there are several “obvious” gaffes to scrub from the Web before you go job hunting, Honaman says, including “inappropriate photos, excessive alcohol/partying, poor language and disparaging comments about current or prior employers, managers or peers. These all indicate a lack of judgment that many potential employers may want to avoid.”

You’ll also want to disassociate yourself from any risqué e-mail addresses, such as Hotmama@gmail.com or party24x7@aol.com. “You wouldn’t believe some of the things I’ve seen,” Honaman says.

Plus, you’ll want to be vigilant about monitoring the privacy settings on all the social networking sites where you have memberships. Facebook, for example, was faced with a tsunami of member anger a few months back when it decided to make more of members’ private information public—without first consulting the members on that move.

Facebook has since mostly rolled back that privacy breach, but the move clearly demonstrates that the information you think is safely stored behind digital walls online could become public at the whim of a new, often young, CEO.

Flanders’ Webster also advises that evidence of an extremely positive reputation online can translate into a real plus. “Credible connections, community service links, positive posts without significant amounts of personal details of their lives—evidencing that they can separate personal from professional,” is what she looks for.

Roach Howard’s Farris agrees: “My advice would be to build a large networking base and ask people to provide recommendations, such as LinkedIn. You might want to consider a separate Facebook account for personal use and LinkedIn for professional.”

Pew Internet also reports that at least some Web socializers are becoming more conservative with the privacy settings on the sites where they gather. A full 71% of social networkers aged 18-29 have tightened up on their privacy settings online, the research group found. And another 55% of users aged 50-64 have done the same, according to “Reputation Management and Social Media,” the company’s survey on social networking released this past May.

Many of these same users have also taken the time to delete unwanted comments that others have made on their Web profiles and have removed their names from photos of themselves that family, friends and colleagues have posted online. Other tools shown for polishing an online reputation are shown in the accompanying sidebar.