"And the LORD said, Because the cry of Sodom and Gomorrah is great, and because their sin is very grievous; I will go down now, and see whether they have done altogether according to the cry of it, which is come unto me; and if not, I will know." (Gen. 18.20-21)
Notice that God says that He has heard ("the cry of it") of the evils of the cities of Sodom and Gomorrah.
I'd always assumed that "the cry" was God's general omniscience coming into play.
I'm not so sure, especially when comparing the Genesis 18 passage with that of 2 Peter:
"And delivered just Lot, vexed with the filthy conversation of the wicked: (For that righteous man dwelling among them, in seeing and hearing, vexed his righteous soul from day to day with their unlawful deeds)." (2 Peter 2.7-8)
Is this perhaps an early instance of imprecatory prayers prayed against evildoers? (In this case, Lot praying about the cities in which he dwelt).