“‘Truth is cheap, but information costs.’ I can’t remember who said that.”
“Vince What’s-His-Name,” said Sam. “Died in a terrorist raid or something. I thought you said all information should be free.”
“It should. It isn’t. Knowledge is power. But power corrupts. Which means the Age of Fast Information is an extremely corrupt age in which to live.”

As quoted in "Humanity will survive information deluge — Sir Arthur C Clarke" in OneWorld South Asia (5 December 2003) http://southasia.oneworld.net/article/view/74591/1
2000s and attributed from posthumous publications

Source: Americanah (2013)

Source: The Postman (1985), Section 3, “Cincinnatus”, Chapter 14 (p. 267)
Variant: It is said that power corrupts, but actually it’s more true that power attracts the corruptible. The sane are usually attracted by other things than power.
As quoted in Values of the Wise: Humanity's Highest Aspirations (2004) by Jason Merchey, p. 120
This is very similar to the expression by Frank Herbert in Chapterhouse: Dune (1985): "All governments suffer a recurring problem: Power attracts pathological personalities. It is not that power corrupts but that it is magnetic to the corruptible. Such people have a tendency to become drunk on violence, a condition to which they are quickly addicted."
Context: It’s said that “power corrupts,” but actually it’s more true that power attracts the corruptible. The sane are usually attracted by other things than power. When they do act, they think of it as service, which has limits. The tyrant, though, seeks mastery, for which he is insatiable, implacable.

Page 285.
Your Right to Know: A Citizen's Guide to the Freedom of Information Act, 2nd Edition

Source: Colorless Tsukuru Tazaki and His Years of Pilgrimage

Source: The Age of Missing Information (1992), p. 9

Sec. 23
The Gay Science (1882)

As stated in, Warrants and Computer Searches. http://jayleiderman.com/blog/jay-leiderman-quoted-part-6-warrants-and-computer-searches/
Variant: The warrant did not give the power to rummage through the journalist’s files,” Leiderman said, adding “there is no indication of why all this information needed to be seized.

Source: The Ordeal of Change (1963), Ch. 2: "The Awakening of Asia" This passage uses phrases from his earlier work The Passionate State Of Mind, and Other Aphorisms (1955)
Context: It has often been said that power corrupts. But it is perhaps equally important to realize that weakness, too, corrupts. Power corrupts the few, while weakness corrupts the many. Hatred, malice, rudeness, intolerance, and suspicion are the faults of weakness. The resentment of the weak does not spring from any injustice done to them but from the sense of inadequacy and impotence. We cannot win the weak by sharing our wealth with them. They feel our generosity as oppression. St. Vincent De Paul cautioned his disciples to deport themselves so that the poor "will forgive them the bread you give them."