After interviewing a college student in June, Tory Johnson thought she had found the qualified and enthusiastic intern she craved for her small recruiting firm. Then she received the candidate's thank-you note, laced with words like "hiya" and "thanx," along with three exclamation points and a smiley-face emoticon.

"That email just ruined it for me," says Ms. Johnson, president of New York-based Women For Hire Inc. "This looks like a text message."

Hiring managers like Ms. Johnson say an increasing number of job hunters are just too casual when it comes to communicating about career opportunities in cyberspace and on mobile devices. Thank yous on paper aren't necessary, but some applicants are writing emails that contain shorthand language and decorative symbols, while others are sending hasty and poorly thought-out messages to and from mobile devices. Job hunters are also using social-networking sites like Facebook and MySpace to try to befriend less-than-willing interviewers.

These incidents typically involve college students and recent graduates, and recruiters say such faux pas can be instant candidacy killers because they hint at immaturity and questionable judgment.

The trend may reflect a cultural divide between younger and older workers, says David Holtzman, author of "Privacy Lost: How Technology Is Endangering Your Privacy." "It's driven by the communication technology that each generation has grown up with," he adds. Workers in their 20s and younger are accustomed to online and cellphone messaging, and the abbreviated lingua franca that makes for quick exchanges, he says. "It's just natural for them. They don't realize that it's perceived to be disrespectful."

Travis Hawk, a May graduate of Drake University, says he prefers sending text messages to making phone calls and almost fell victim to his text-lingo behavior in emails to recruiters during his recent job search. "I had to focus on not doing it," says the 23-year-old, who just got an entry-level sales position at Principal Financial Services Group. Now an intern at the Des Moines, Iowa, firm, he says his penchant for using abbreviations such as "r" for "are" is sometimes hard to manage. "Occasionally, on accident, I throw one in an email at work," he admits.

Other job hunters, however, don't see any need for restraint. Consider, for example, that smiley faces, hearts and other icons appear in about one of every 10 thank-you emails sent to hiring managers at KPMG LLP, says Blane Ruschak, the New York accounting firm's national director of university relations and recruiting.

But KPMG's staffing specialists, who hire about 2,700 college graduates and 2,300 interns annually, aren't amused. "We don't feel emoticons have a place in any formal communications," says Mr. Ruschak. "It's not professional." And seeing them makes KPMG's hiring managers wonder whether that sort of unprofessional communication will follow the applicant to the workplace. Graduates who commit the offense may lose out on a job if "there are other candidates similar to them that didn't," he adds.

On-the-Fly Mentality

Some job hunters are earning the rebuke of recruiters by taking thank yous to another extreme -- by sending them hastily from their mobile phones. The move suggests an on-the-fly mentality, as if the applicants haven't taken time to think about why they want the job or why they are saying thanks, says Wendi Friedman Tush, president of Lexicomm Group, a boutique communications firm in New York. "It always says 'From my Blackberry,' " she says. Candidates "should sit down at their computer in a thoughtful way and do it, not while they're on their way somewhere," she says.

Executive recruiter Hal Reiter recently received such a thank you from a chief financial officer candidate sent by BlackBerry just minutes after the interview. "You don't even have time to digest the meeting and you're getting a thank-you note," says Mr. Reiter, chairman and chief executive of Herbert Mines Associates, a New York-based search firm.

This year, hiring manager Cathy Chin received a thank you on her cellphone from a candidate for an entry-level job at ReThink Rewards Inc., a marketing firm based in Toronto. While she says her cell number is on her business card, which she gave to the candidate, all prior correspondence had been through her office phone and email. "It's infringing a bit on your personal space," she says, adding that the candidate wasn't hired partly for this reason.

Interviewer as 'Friend'

And a candidate for an assistant account-executive job recently sent a "friend" invite to Ms. Friedman Tush on her personal Facebook page following an interview. Her company doesn't have a page on the social-networking site. "I'm not his friend. I'm not even his employer. I was somebody who interviewed him," she says. "They are called social-networking sites for a reason."

Job hunters may be more inclined to use their cellphones and text lingo when thanking interviewers because the medium is gaining acceptance in a growing number of workplaces. "I definitely text my managers if I am running late," says Jennifer Nedeau, 23, a project manager at New Media Strategies Inc., a marketing firm in Arlington, Va. "I know I'm not bothering them with a phone call, but they're still getting the message."

Are there ever exceptions to sending a thank you through a mobile phone or social-networking site? Perhaps if someone is applying to a company that sells or relies heavily on the technology, say hiring managers. But Ms. Johnson points out that it may be less effective than email since recruiters can't forward these types of messages to colleagues as easily.

The younger set sees the world of interview and workplace language evolving. Chris Brubaker, a junior at Iowa State University, predicts that "textspeak" will soon become accepted in the workplace. "Text messages are much more short and to the point," says the 20-year-old. "General communication is becoming more electronic."

Indeed, employers themselves are blurring the lines to some extent by using mobile and Web technology for recruiting, including posting job ads on social-networking sites like MySpace. Ms. Chin's firm has a Facebook page that lists information about job openings and its work environment. For this reason, Ms. Chin says she doesn't mind getting thank-you messages through the site's email system. The effort can even help a candidate stand out. "It puts a face to the name because it shows your profile picture," she explains.

Still, Ms. Chin says there's no excuse for using shorthand in messages to recruiters. "A thank-you note -- even if it's on Facebook or email -- should be written like a proper letter," she says. "If I'm going to give you a job, do I really want you communicating to our clients in this fashion? No."

Write to Sarah E. Needleman at sarah.needleman@wsj.com