Text (4th+errata): All Swamps are 1/1 creatures that are still lands. [Oracle 2003/07/01]
The creatures are not black. [D'Angelo 2000/03/03]
It affects Swamps controlled by any and all players. [D'Angelo 1994/03/01]
The Swamps are both lands and creatures at the same time. [D'Angelo 1994/03/01] They are affected by anything that affects either permanent type. For example, Wrath of God and Armageddon or Smoke and Winter Orb.
With Balance, consider them both as lands and as creatures. Just remove whatever you have to in order to achieve "balance". And yes, this does mean that they get double-counted :-( [D'Angelo 1994/06/01]
Extended tournaments (see Rule 913) have banned this card since 1999/10/01.
