I mentioned before how I'm not a fan of LinkedIn:
I’m not a fan of LinkedIn, as it seems to be mainly a way to get harassed by recruiters who didn’t even bother reading my profile.
Some number of years back, I added the following clause to my LinkedIn profile:
Recruiters: if you contact me, please specify the position you are recruiting for, what city it is in, and whether you can meet the above asking salary. Please include the word PINEAPPLE (all caps) in your communication.
In the five or so years since I placed this clause, none of the dozens of recruiters who have contacted me via email or phone call or even via just sending a connection request on LinkedIn itself has ever complied with this clause in any way.
I've seen people using LinkedIn from the other side - looking for candidates to fill positions - and most of them will just quickly skim your profile to see if you tick all the checkboxes of what they're looking for. Recruiters and other people looking to hire have to sift through lots of resumes and profiles and very few will bother to go through your entire history.
Overall, I am not convinced that LinkedIn is at all useful or that it has been a net positive for me personally, but I still have a profile and sometimes post my blog entries there. Also, given that I want to reduce Facebook usage, it's probably a good idea to have work-related contacts on LinkedIn instead of Facebook moving forward.