Draconian password schemes lead to really insecure user behavior. For example, an iTunes account requires upper-case, lower-case, and a number; but it doesn't tell you that until you try "insecure" passwords. So I bet a lot of users, feeling really frustrated, just use their name (capitalized), and birthday, rather than the semi-secure password the they wanted to use (or in my case, a fairly strong pass-phrase with no numbers).