1. LinkedIn has over 135 million members in the United States and 3.3 billion members globally, making it a significant professional networking platform. 2. The document discusses using LinkedIn for professional networking and marketing purposes, such as promoting one's law practice to the over 1,700 LinkedIn members in the Minneapolis area legal field. 3. It also briefly mentions metrics like 43,000 print subscribers and research showing that asking for retweets generates 4 times more retweets than not asking.