A little while ago, LinkedIn began allowing members to endorse each other. Unlike recommendations, endorsements were simply a way for one member to confirm that another member has a particular skill. Because LinkedIn made it extremely easy to quickly endorse people for multiple skills, and because there is no verification required at all, many observers questioned the validity or use of the feature, myself among them.
Of course, it's nice to have a great list of skills on your profile, and having tons of endorsements for your skills is certainly more impressive than none at all. Furthermore, each time you endorse a potential partner or prospect, that person gets a nice email telling them that you thought they deserved to be endorsed for some skill.