Balance should be maintained between how much time should be spent for computers and other different activities. Children should be encouraged to be outdoors. However they also need to use computers, parents should put their children onto computers but also make sure that they take part in extra curricular activities. I feel children should be exposed to computers at a young age. The art of teaching while playing games is the best suited for childern this age.
Computers can teach various concepts to the children at different age levels.
As toddlers too the children develop eye hand coordination, learn to appreciate music etc. So introducing computers is beneficial at an early age as long as the amount of time they spend on the computer is age appropriate. You will be amazed at the grasping power of young chilcren. And in fact, the more they are stimulated and challneged the more they learn. There are so many games now for kids below the age of 3 that are educational and at the same time fun.