LinkedIn has announced that it has reached 50 million users. Highlighting its continuing growth, the company noted that it took almost a year and four months to notch its first million users after launching in 2003, but only 12 days to add its last million. The company also said that about 1/2 of its users were international, with 11 million in Europe. India is the fastest-growing country with almost 3 million users, while the Netherlands has the highest rate of adoption per capita outside the U.S., at 30%. More details at MediaPost.