classic but still valid.
No, see
http://www.wired.co.uk/news/archive/2013-05/28/password-cracking Passwords like "momof3g8kids" were cracked. Modern password cracking programs do dictionary attacks with multiple words and arbitrary characters between words. So four common words (maybe a dictionary with 1000 common words) would need 1000^4 = 10^12 tries. Depending on the algorithm, modern graphics cards or special hardware can test 10^9 passwords per second, which means it would be cracked in 17 minutes. A three word password in one second, which allows even testing for the popular number or character between the words.
The only secure password is at least 10 random letters and numbers. Anything random below 8 could be cracked fast, if the system uses standard hashing functions and if the hacker has the password hash.