Getting inside the White House uninvited

Imagine what could be one of the most secure locations in the world ? The White House would be one of these locations, one would think of locations such as those housing huge sums of money, those housing the secret of Coke's formula, and also those housing nuclear weapons; but there should not be any comparison with the White House. The White Houses the most powerful man in the world, who commands a huge army and holds the key to the economic well being of the world. And in such a secure place, the thought that people could gate-crash and get inside may seem incredible, but it is the truth.
This has left the Secret Service totally red-faced, after all, they are responsible for the security of the American President, and the fact that somebody was able to get inside even though they were not invited is a horrible security breach (link to article):

A White House photograph taken Tuesday evening shows Michaele Salahi, wearing a gold-accented red sari, clasping her hands around Obama's right hand as her smiling husband, Tareq, looks on. The dinner was held for visiting Indian Prime Minister Manmohan Singh, who is smiling next to the president in the photo. An investigation into Tareq and Michaele Salahi has found that Secret Service agents did not follow protocol at a security checkpoint, the Secret Service said.
The Secret Service's statement says that although the Salahis went through magnetometers and other levels of screening, "they should have been prohibited from entering the event entirely." "That failing is ours," the statement said.