Yes, it is possible to lose a jetliner with the technologies available in 2014, because the missing flight is proof that it can happen. They do not know where that airline went. As soon as the pilot switched off the transponder, we had no way to track for sure where the flight went.
Yes, I believe that even with the technology we have in 2014 it is still possible to lose a jet airliner. I think a big part of what happened here was that searches were not implemented immediately. I think too much time was spent on speculation. There seemed to be a lot of chaos surrounding this event and no one in authority to coordinate things.
Yes even with the tracking technologies available today it is possible for an airliner the size of a Boeing 777 to go missing if the crew doesn't want it found. All of the technology used for tracking commerical aircraft it dependant on actions of the crew. Transponders, ARCS, satellite communications can be disabled by the crew making the place a virtual 'hole in space.'
I'm not sure what more proof we need to say this is true. The missing airliner has been gone for weeks, so it's obvious that we can lose one with today's technology. It would seem we over estimate the coverage of satellites, but why would we cover the oceans anyway?