For self-serving purposes, Syria in particular has riled up people locally as well as in Lebanon. Foreign embassies are set on fire with implicit government permission.
The other thing to remember is that Muslims feel like they have been under attack for a while and especially since 9/11. So there as a lot of ill will ready for ignition and it would be wrong to blame the cartoons for all the violence. The cartoons were the match that set off the abundant kindling.