1 billion endorsements have been given to 56 million LinkedIn members

"Are you one of the 58 million professionals who have been recognized for their skills and expertise on LinkedIn? Skill endorsements are a great way to help build your professional brand, in fact you’re 4 times more likely to be viewed on LinkedIn if you’ve been endorsed. It’s also an effective tool to recognize the wonderful strengths of your colleagues and peers who you’ve worked with first hand.
In less than six months, 1 billion endorsements have been given out on LinkedIn representing thousands of skills, ranging from Visual C++ to Water Treatment and Creative Writing to Fitness. Did you know giving and receiving endorsements also helps members beef up their profiles? Not only have we seen a 2x weekly increase in recommendations since the launch of endorsements, members are also actively adding new skills to their profiles to showcase their full expertise. Not to mention the many, many coffee dates we know are being scheduled as a result."

Source:  Blog post from LinkedIn, 6th March 2013