When LinkedIn Endorsements were rolled out last fall, they were greeted with a collective "Huh?" followed by widespread disdain. The "Huh?" was a response to the surprise nature of the feature -- no one saw it coming, and LinkedIn didn't do a lot to explain it. The disdain rose up from the tit-for-tat nature the feature took on: You endorse me and I'll endorse you. Some people resented that people they barely knew were endorsing them for skills the endorser had never experienced first-hand.
No matter how you feel about Endorsements, they appear on your profile, and you want to make sure that any Endorsements you have are in the skill areas most important to your current -- and especially future -- job. Providing genuine Endorsements to others is a good way to get endorsed authentically.