Some time ago I read somewhere that Microsoft had problems getting software testers in Denmark. They were puzzled by this as they found the workforce to be educated and they had no trouble finding developers.
Although testers and developers should share some common knowledge of technology, their personalities are completely different. Good developers need to be inovative to be able to find solutions to problem they have never seen before. They should focus on the big picture and always strive for the best compromise. Good testers on the other hand have to focus on details and they need to be able to repeat an exact action and follow a script. The qualities wanted are opposites and it will most likely never be possible to find a person that posseses both.