Crowds of demonstrators celebrated in the streets of Sanaa this weekend over the news that President Ali Abdullah Saleh had left for Riyadh. The Yemeni president is in Saudi Arabia to seek medical treatment following a rocket attack on his palace that left him and several senior officials injured. There is intense speculation over the seriousness of Saleh's injuries and whether he will return, but for the time being it appears Vice President Abd-Rabbu Mansour Hadi has taken over. The White House says President Obama has spoken with Hadi, an indication that Hadi is in fact in charge. Even if Saleh doesn't return, Yemen's troubles won't be over. He left behind his son and onetime heir-apparent Ahmed, who commands the presidential guard and who met with Hadi last night.