I have found that Facebook groups, email forums, twitter slow chats, and good old face to face opportunities have been much more profitable for my PLN. I understand that many find huge value in sites like LinkedIn but as Mary mentioned above while there are a lot of librarians one linkedIn it's not really a place to job search. I also, due to my current job am constantly learning new skills. Because of this (and grad school) I have had to limit my social media consumption/accounts to a more manageable number for the time I now have available. I don't really miss tumblr, after the yahoo purchase I feel the commercialization and the weird new interface ruined the experience for me. I do miss twitter, however, twitter is a "time suck" and to keep abreast of topics and conversations you should be logging in more than once a day.
As a public librarian I also feel it's really important that we are able to understand how these sites work, as well as how to best present our users to their future employers. As a School Media Professional I would imagine this would be a very important skill to teach to your students. Digital Literacy is important on both for professional (job skills, job search, professional digital footprint) and personal (digital footprint, potential job connections) and we have to make sure our students understand the difference. I have know to many kids that lost jobs or potential jobs due to content employers viewed on their social media sites.
Moreno, Mary . "Do I have to use LinkedIn?" Learning at the Library. N.p., 05 Mar. 2017. Web. 14 Mar. 2017.