It is completely useless in the sense that you can do the same thing with a simple blog and json file for your resume. The reason people use it is because it is an extremely simple way to showcase a professional profile in a place where every recruiter and their grandma knows is full of professional profiles.
It would be very easy to build an alternative. The hard part would be amassing the critical mass of recruiters. For a while Forrst was on the right track but it no longer exists.
I didn't take linkedin seriously until I lost my job. Having an upto date profile on LinkedIn does 2 things:
* lets recruiters see everything about you in one place
* suggests related jobs
Now, the story of how I got my current job: met guy at local Meetup, talked to him a bit and found out the company was hiring, and he would mention my name to recruiter. So, I add him on linkedIn, but get no call whatsoever from any recruiter. I see that there's a company recruiter on his connections and add her; explaining that I had met so and so at a meetup and there is an opening for a person with my skills so would she be kind enough to set me an interview? It takes some time, but I do get the interview, clear it, and all the other interviews as well.
I know of at least one blue chip firm that no longer pays headhunters, and now does all their recruiting via LinkedIn using the paid Recruiter features.
It would be very easy to build an alternative. The hard part would be amassing the critical mass of recruiters. For a while Forrst was on the right track but it no longer exists.