In order to highlight what happens when an alien lies on a visa or immigration petition, allow me to cite the example of Inocente Orlando Montano, a citizen of El Salvador. He applied for temporary protection status (TPS) in the United States and in order to be eligible for the program, he deliberately entered the wrong date of his entry into the US. He also hid record of his military service. While tens of thousands of immigrants in USA are able to fool the authorities, Montano was convicted of immigration fraud and perjury. He is now in prison and after doing his time he will be deported to El Salvador. If you decide to lie on an immigration petition or provide a false document you should be prepared for similar punishment.
It is understandable USCIS makes mistakes and some people are just too good at committing fraud. In many countries from which most of the immigrants come, it is easy to get almost any type of fraudulent document for the right price or if you know the right people. Now if you are tempted to lie on your immigration application or provide a fraudulent document, you may want to think again. While so many applicants get approved, it does not mean that they might never be apprehended. It is important to remember that even naturalized citizens can be stripped of their citizenship if they resorted to fraud during their immigration journey. Of course, visas and green cards can be nullified very easily at any point. Prison time for several years and then deportation are standard procedures.