Is the Apophis asteroid a concern for planet Earth? I was watching the TED lecture How to defend Earth from asteroids , and the speaker Phil Plait spoke of the possibility of this asteroid hitting Earth. Is this really a concern?
Apophis is of no real concern to us as far as we can tell.  That said, it doesn't mean another asteroid doesn't have our name on it...

According to the most reliable data we have regarding this particular asteroid it only has a 1 chance in about 250,000 of hitting the earth.  University of Hawaii states:


  “Our new orbit solution shows that Apophis will miss Earth’s surface in 2036 by a scant 20,270 miles, give or take 125 miles,” Tholen said. “That's slightly closer to Earth than most of our communications and weather satellites.” He credits the large telescopes and superb atmospheric conditions on Mauna Kea for being able to make these determinations.


Considering how big space is, this is pretty much a hit in cosmic terms.  Keep in mind that this information has been readily available since 2009 at the NASA website as well.