No. It is not common, but it is serious.
A complex question. There are three main types of cardiomyopathy. Hypertrophic cardiomyopathy is quite common and is hereditary, with an incidence in the u.S of 1 in 500 people, and is a cause of sudden death. Dilated cardiomyopathy is usually the consequence of coronary artery disease, or of a viral infection (more common in young people), and is difficult to quantify. Restrictive cardiomyopathy is extremely rare.