Earlier quoted context omitted.
I work at LinkedIn, we actually do use skills in a number of places (like the job pages); typically they are used more of a "here's how your skills compare to other people's" and less of a "you'll get hired if you have skill X listed". We know people can game them, so we try to only use their skills in ways that would be helpful if their skills are actually real to give less incentive for people to lie.
As implemented, they're basically useless. Asking "does X know about Y?" without verifying that I have any knowledge of Y myself doesn't do much. My dentist has endorsed me for things like "Cloud", and while he's a great guy and good at his job he can barely work his iPad. I personally view those as noise at best and very skeptically at worst -- if someone has a bunch of endorsements for a particular skill I suspect…
I disagree with your reasoning here. While I agree endorsements are useless, I also believe that makes them more or less meaningless. I don't think jumping to conclusions based on endorsements, weather positive or negative, is a good idea.