Well, my experience with LinkedIn has been very different. To start, I don't have my mom in my LinkedIn! Not only I have found my current job from LinkedIn, I also regularly received interview invitation for positions from other companies (from large scale ones like Google, FB, Amazon, etc. to smaller companies).

But to me the best advantage of LinkedIn is it helps separate professional relationships/conversation separate from my personal life. My contact network at LinkedIn showing my professional connections is very different than my contact network in Facebook, and while I use both, I don't want them to be mixed.

Plus, it keeps my CV and I don't have to always look for my CV in bunch of doc files if I have to send it to someone.

Maybe you would have a different experience if you would spend more time on setting it up? (writing the CV, adding the right people. etc)