People who worry about dangers of AI understand that too. However, figuring out how to make a safe AI may be much harder than building a powerful enough AI in the first place, therefore they argue it's worth to start working on AI safety now.
Frankly the use of the word "intelligence" to describe advanced pattern recognition algorithms is pretty laughable. Nobody is even close to anything the involves actual thinking / learning. I think your day jobs are safe.
http://observer.com/2015/08/stephen-hawking-elon-musk-and-bi...
Which makes sense. The opinion of everyone I know that has actually worked with machine learning and state-of-the-art AI (as in, written code, ran experiments, etc.) is that the idea of today's AI suddenly waking up and taking over the world is utterly ridiculous, or at least not something we should be afraid of for the foreseeable future.