Do you think computers have capacity to take over the world / why or why not?

Not by themselves. They've yet to have what we'd consider even rudimentary intelligence. There is, however, a great power and reach in the network infrastucture we've created between computers. In 25 years time, wars will not be fought by soldiers and bombs but via the internet. We will be so dependent on our network for money, entertainment, even water, electricity and food, that deny a nation that network is effectively laying siege to an entire country.

There will, of course, also be individuals or groups who abuse the network. Digital terrorism will one day be a reality. The roots of it are already here:

http://www.bbc.co.uk/news/world-us-canada-22470299

As for computers themselves acting with a consciousness to gain primacy over humans, I don't believe it will ever happen because I don't think humans have long enough left on this planet for technology to develop so far. Besides that, humans are pretty intelligent, numerous and resourceful.

Computers are man made and are intended to help us humans with different technological tasks. I in my opinion think it wouldn't be possible unless, some one made and programed a computer to rule the world and it's people. So no I don't think it could happen in this day in time but it could possibly happen in the future.