The sense of alienation that an immigrant community may face in a country can drive the members of the immigrant community to drastic measures like this. It's a pity I cant post nytimes links here (requires registration and articles older than 2 weeks are archived for a pay-only service), but Tom Friedman had a couple of very good articles analysing this scenario (now, who isn't analyzing this scenario these days, even *I am*!) which resonated with my thoughts on it too.
Suketu Mehta (who, if I may show off, I met during a film-festival, where he introduced the movie, Bombay, and stayed on to speak with some of us after the show), an Indian author, had a real good op-ed piece where he said the US could use the Indian immigrant community here help them understand the psyche of the Indian commuity in India (with reference to why American jobs are going overseas to India and what we have to do better/differently here in the US) and similarly, the muslim immigrant community could help us understant the psyche of the muslim communities all over. To stereotype and typecast may be one of the most dangerous things at this point.
Every muslim doesn't wanna blow up people - the greatest majority are god-fearing, simple people like you and I who would rather take a subway without the fear of getting blown up. I sincerely believe that a solution lies in not just searching through bags in the subway, but striking the problem at its root, and understanding why someone would wanna do what they do, and addressing that issue. Wonder if it'll happen though..
In the same ballpark of immigrant communities, a great movie I saw recently, Crash - big cast; good acting; strong, powerful dialogues and punch-lines. It beautifully explores the typecasting and stereo-typing that happens in societies all over and without being preachy, very subtly gets the point through.