The discussion is a bit similar to why people decide to act out a terrorist attack. There's been tons of research on this, it's hard to pin down and it's very individual related. Bad economy and low education definitely play a role, but there's more to it. There's plenty examples of college-graduates doing the same thing. The factor that seems to come back is: detachment from society. That can mean unemployement, but can also be ideological, feeling left out, frustration, humiliation.

And the attack on the embassy in Libya was almost certainly a planned attack, not a sudden riot. Of course certain groups are going to try to take advantage of this.