Definition of flaw | Bee Dictionary of English

n an imperfection in an object or machine
a flaw caused the crystal to shatter
n defect or weakness in a person's character
he had his flaws, but he was great nonetheless
n an imperfection in a plan or theory or legal document that causes it to fail or that reduces its effectiveness
v add a flaw or blemish to; make imperfect or defective

According to Flesch, the basic flaw in the system lies in that it "looks at a child as if it were a small-size adult.
The other flaw is this attitude of holier than thou.
This is the flaw that makes Jem interrupt the boasting of a lineage-proud dowager to ask "Is this the Cousin Joshua who was locked up for so long?".

Facebook flaw reveals some personal data from 6 million users
Facebook's "White Hat" hacker program has exposed a vulnerability in the social network's "Download Your Information" tool. According to the company's security blog, a flaw allowed users (but not developers or advertisers) to farm phone numbers and email addresses attached to friended-users Facebook accounts....
June 22, 2013 - MacNN
Facebook Says Technical Flaw Exposed 6 Million Users
Because of a flaw, Facebook users who downloaded contact data for their list of friends obtained additional information that they were not supposed to have.
June 21, 2013 - New York Times
Facebook flaw exposes info of 6 million users
Facebook Inc. says a flaw may have exposed portions of the personal contact information, such as email addresses or phone numbers, of roughly 6 million users.
June 21, 2013 - The Alexandria Town Talk

Pervez Musharraf in USA Today
One should not give a statement that's 100% final. That's the flaw that we suffer from,Musharraf said, noting that more evidence was emerging on the attack. "We needed more experience, maybe more forensic and technical experience that our...
Alan Greenspan in International Herald Tribune
Greenspan called that "a flaw in the model ...... that defines how the world works."
David Caplan in Hamilton Spectator
We have a system that provides universal coverage,Health Minister David Caplan said. "The flaw in the American system is that first they check the size of your wallet, not the size of your need."