I've written about Facebook job postings before:
How-to-hire-salespeople-using-Facebook
Using-facebook-to-recruit
Why-facebook-will-destroy-linkedin
Is-facebook-about-to-offer-free-job postings

Now it looks like Facebook is serious.
Will it work. Yes.
Will it kill all other sites including LinkedIn? I believe no.
No matter how integrated our media becomes, there will still be a desire on behalf of many people to keep their private and professional lives seperate.

What does Forbes have to say? Read below:
Thanks!
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Facebook Jobs Could Kill LinkedIn's Momentum

Trefis Team, Contributor Forbes Magazine

Facebook is apparently working on a job postings board that will launch later this summer, according to a report by the WSJ. “Facebook Jobs” will be an aggregator that pulls in job postings by third party providers and makes them available in one place and creates a searchable database of jobs for users to browse.

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Facebook could also use the tons of social data it has on each user to target relevant jobs across its vast network of users as well as provide an excellent recruiting solution to corporate clients and placement agencies, which will compete directly with LinkedIn. ^[1]
Check out our complete analysis of Facebook
We have already seen how Facebook’s social graph can be leveraged by job posting and recruitment apps like BranchOut, JobVite, Work4 Labs and Glassdoor. These apps have attracted millions of users in months thanks to the inherent viral nature of the network. Facebook is not cutting them off, but rather partnering with them to become a comprehensive social recruitment solution.
While Facebook plans to use the job postings service to rack up engagement metrics initially, it could definitely look to monetize it eventually. This could open up yet another revenue source for Facebook, which is dependent primarily on social ads and virtual payments at present.
Facebook has more than 900 million monthly active users while LinkedIn has close to 150 million. If Facebook does this right, it could take away a meaningful amount of recruitment dollars away from LinkedIn. This could be one of biggest threats that LinkedIn has faced until now.
LinkedIn, beware.
We currently have a $33 Trefis price estimate for Facebook, which stands just above its market price.