Hitwise is reporting today that Twitter has passed Digg in the number of weekly unique visitors for the first time ever. Social media sites including Twitter have experienced a surge in traffic over the past week with people flocking to the sites to get more information from big events, including the US Airways Hudson River crash, and the inauguration of Obama. Now, it is important to note this is only for weekly visitors, according to Compete, Digg got almost 35 million visitors in December 2008, while Twitter had only about 4.4 million. Nevertheless, Twitter is certainly surging in popularity.