My informal survey suggests that LinkedIn may be the most popular social media website among seasoned professionals. Harder evidence of LinkedIn’s indispensability: According to a Jan. 27 New York Times article, “In Hiring, a Friend in Need Is a Prospect, Indeed,” some large companies are finding qualified candidates by recruiting new hires from the LinkedIn networks of their current employees. In the process, they are bypassing reams of nameless applications from recruiters and job boards. So if you’re seeking a nonfederal job, it is practically de rigueur to create an impressive LinkedIn profile. And if you’re seeking a federal promotion, the same is…