Just for completeness, in case someone doesn't know about it, the Anna Karenina principle (first time I've heard it called this) refers to the first line of the Tolstoy book of that same name:
The Anna Karenina principle was popularized by Jared Diamond in his book Guns, Germs and Steel to describe an endeavor in which a deficiency in any one of a number of factors dooms it to failure. Consequently, a successful endeavor (subject to this principle) is one in which every last one of the possible deficiencies has been avoided.
http://www.penguinclassics.co.uk/nf/shared/WebDisplay/0,,489...
'All happy families are alike; each unhappy family is unhappy in its own way.'