Senegal has for long been considered a model democracy, a reference for Africa and the Muslim World. But nothing is perfect and certainly the former French colony has many issues including widespread poverty and lack of expectations, a common problem nowadays in most of the World but specially in Africa.
What has triggered these riots was the attempt to reform the electoral aspects of the constitution, allowing a candidate for president to win in first round with as little as 25% of votes. Additionally it created the office of Vicepresident, which was suspected would end in the hands of the President's son.
The current President Abdoulaye Wade is 85 years old and seems to be thinking more in his son than in his country.
All this made the Senegalese People to go out to the streets to protest, chanting "Leave Wade" and "Don't touch my constitution", protests that were violently attacked by police forces:
Anyhow, part of the controversial law has already been dropped.
Sources: Al Jazeera, Protestation.org.