Why did dinosaurs go extinct?

Source: Gary Larson–The Far Side

Watch this short movie to help better understand the reasons dinosaurs died out, and why it matters to us today.

There are various reasons why dinosaurs (and other animals) became extinct.  One theory is that dinosaurs may have terrorized people and eaten their cattle or other farm-raised animals, so people hunted them to extinction.  Another theory is that they ran out of food and began to kill each other.  Still another theory is that the climate affected their survival.  There are several other reasons why animals become extinct today and those reasons can easily apply to the dinosaurs of the past.  Maybe the endangered species program should have started earlier?