News leak
[1] Leaks are often made by employees of an organization who happened to have access to interesting information but who are not officially authorized to disclose it to the press.
A leaker may be doing the journalist a personal favor (possibly in exchange for future cooperation), or simply wishes to disseminate secret information in order to affect the news.
This may also be intended to allow journalists more time to prepare more extensive coverage, which can then be published immediately after the official release.
[3] Some leaks are made in the open; for example, politicians who (whether inadvertently or otherwise) disclose classified or confidential information while speaking to the press.
[4] Most immediately, fear of further leaks after the Pentagon Papers were published in 1971, such as of the Secret Bombing of Cambodia, led to the formation of the "White House Plumbers" unit (so named because they wanted to fix leaks), which conducted the break-in that led to the Watergate scandal and Nixon's eventual resignation in 1974.
James Marshall's discovery of gold in the South Fork of the American River at Sutter's mill on January 24, 1848, started the great rush of Argonauts to California . Marshall and Captain John Sutter tried their best to keep the discovery of gold quiet until the construction of Sutter's mill was completed, well knowing that the workmen would desert their jobs and turn to digging gold. The news leaked out, and the stampede began.