2010-08-15
The ability cares about lands with the land type Swamp, not necessarily lands named Swamp.
2010-08-15
This ability counts the number of Swamps controlled by Quag Sickness's controller, not the enchanted creature's controller (in case they're different players).
2010-08-15
This bonus is not fixed; it changes as the number of Swamps you control changes.