There are 3 million “skilled” writers on LinkedIn. This story isn’t written by one of them.

Since allowing users to designate skills — and be endorsed for them — five months ago, LinkedIn’s members have given out 1 billion endorsements. If those recommendations are to be believed, the professional social networking site could transform what was traditionally one of the more boring sections of a resume into one of the most dynamic. “Skill endorsements are a great way to help build your professional brand,” a LinkedIn US:LNKD spokeswoman says.

Linkedin offices. Adam Barker/Linkedin

But now that users have been endorsed for so many skills, as LinkedIn announced on Wednesday, some recruiters are skeptical. Either LinkedIn members make up one of the most talented groups on the planet or they all have one skill in common: self-promotion. Are 13 million users really skilled at “management,” the site’s No. 1 skill, or are 3 million really skilled public speakers? And should anyone brag about badminton?

Indeed, some HR pros say these endorsements aren’t so useful. What your friends say about you is about as reliable as what you say about yourself, says James Thompson, executive vice president of JMJ Phillip Holdings, a human resources consulting firm. That is, not much. “Job seekers plaster buzzwords all on the top of the resume, only to find in the interview that they really were a master of none of them,” he says. (“Creative” remains LinkedIn’s most overused buzzword.)

While the new feature will likely encourage more members to interact, it may also be used with abandon — just like Facebook’s ubiquitous “Like” button. “I have 49 people who endorse me for “talent acquisition,” says Tim Sackett, president of HRU Technical Resources, an information technology and engineering staffing firm in Lansing, Mich. “Professionally, I haven’t even worked with, or for, 17 of those who endorse me — so how do they know I truly have this skill?” Endorsements may be accepted or deleted, a LinkedIn spokeswoman says.

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Acquiring skills can also turn into a game of one-upmanship, Sackett says. “It’s a social media, narcissist thing,” he says. The competition to acquire wacky skills may be fun, but not exactly accurate. “I’ve been endorsed for jump rope, basketball and karaoke, Sackett says. Nice work, if you can get it. There’s just one problem. “I can’t sing, I can barely play basketball and I haven’t jumped rope since God knows when,” he says.

To be sure, the top five endorsements on LinkedIn’s list are staid: strategic planning, customer service, Microsoft Office, project management and recruiting. But many others may exist only in the eye of the beholder: storytelling (267,000), preaching (410,000), fitness (435,000) and wine (298,000). “Anyone who can hum “I’m Too Sexy” can claim singing as a skill,” says Paul Freiberger, president of career-improvement firm Shimmering Resumes. Blame “American Idol,” he says.

That said, some of these skills could prove useful in an interview. When Thompson is interviewing, for instance, he will simply ask them, “Out of all of these endorsements, who really knew your work before endorsing you?” If, say, a skydiving skill endorsement is legitimate, he will ask: “So if I spoke to this person right now about this particular skill, what would they say about you?” The answer can be revealing, he says.