I booked a hotel room before and several times some strangers would swing the door handle knob and tried to opened it.
Opening regular key-card hotel-rooms aren't very complicated, although the trick used in the video is easily preventable by employing a 90-degree angled door-frame, which most modern hotels uses. Skimming the keys, on the other hand, is still easy. Or employing a simple manipulator, for the old plastic cards with holes in them. It takes less than a minute to try all combinations...
Most hotel rooms also have a manual door bolt thingy for when you are in the room and a safe for valuables when you aren't. Ultimately, don't take anything you can't afford to lose. Have backups of your laptop in the cloud etc, be insured for valuables. It's only stuff and while it's awful to robbed and inconvenient to be without the stolen items you have to be a bit "zen" about it.
Very true. Also, depending a bit on which hotel you stay in, the chances of being robbed are rather slim. Also depending on WHERE you are staying, of course. If you spend your time in a fairly decent hotel (4star+), the chances of anything happening, or the hotel making trouble if something does happen, is slim to none. Make sure you have a decent travel-insurance as well, and who cares.