"This is a new era where everyone needs to have a voice, and you want to leave a digital trail of yourself," says Ms. Siff.
After recruiters and job seekers find each other over Twitter, more traditional means of hiring usually take over: Candidates may tweet a link to a résumé or a more complete social-media profile, followed by phone or in-person interviews.
A tweet, she explains, "is the new elevator pitch."
"I watch people interact, learn what their positions are, who their best friends on Twitter are, whether they have a sense of humor. From that you can get a pretty good picture," she says.
Fed up with traditional recruiting sites and floods of irrelevant résumés, some recruiters are turning to the social network to post jobs, hunt for candidates and research applicants.