To be honest, I have a linked it account but I don't use it much. And I guess that I never saw the potential of LinkedIn until they started with LinkedIn Answers. For me, basically, it is a way to expose your knowledge and set yourself as an expert in the field you want to work in, giving security to the possible employer that you would do the job right.
By proving your knowledge, you can also fight for a higher salary since that possible employer can see a return on the investment.
And it can also prove if you have leading qualities or not, your believes and your behaviour and that's always handy for an employer as he can forsee if you will fit in the team.
And then again, as with anything public if you use it incorrectly it can be your doom. And, in this case, the only advantage could be that Facebook, Quora or StackOverflow are more popular and you may be able to minimize the harm...