Enchantment, 3W (4) Artifacts, creatures, and lands your opponents control come into play tapped.1 "Make people wait for what they want, and you have power over them. This is as true for merchants and militia as it is for cooks and couples." -Gwendlyn Di Corci
Illus. Kaja Foglio
Cards enter play tapped. They do not come into play untapped and then immediately tap, therefore they do not trigger any effects due to tapping. [D'Angelo 1998/02/03]
It affects all opponents. [D'Angelo 1999/05/01]
It applies to cards and tokens that are put into play by an effect, as well as ones that are played from the player's hand. [D'Angelo 1999/07/03]
It applies to cards and tokens put into play under your control by an opponent's spell or ability. For example, with Flicker. [D'Angelo 1999/07/26]
Does not affect cards that phase in. [Duelist Magazine #19, Page 30]
Note - In Fifth Edition (and before) it affected just one opponent.