LinkedIn is the Facebook for people you don't want or need to show your personal pictures, information, or non-company-sanctioned opinions to - AKA "work friends" or potential employers.
But seriously, it can be quite a good tool. I use it to research other companies before I consider being contracted or employed there - the dirt I can dig with a friendly "Hello, why did you leave this company, I'm thinking of working there" would make tabloids blush - and it has some fun items as well. This is a good place to polish your own apple, although I agree the Endorsement item is not necessarily a reliable one.
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