The so-called "laptop ban" -- which actually extends to anything larger than a smartphone -- was put into place because of worry of terrorists' increased interest in airlines combined with the concern that a bomb could be placed within a laptop or tablet. Last month, the DHS decided it would not extend the laptop ban, but it would increase security measures for flights originating outside the US. Those enhancements are going into effect starting today.
If you're flying into the US, you can expect a greater scrutiny of your electronics. You may be asked to unpack your carry on bags so security officials can examine these devices. You can also expect more swabbing and bomb-sniffing dogs. And it's going to take longer: CNN reports that Mexican airports are advising that travelers arrive three hours prior to scheduled flights in order to ensure passengers have time to get through the screenings. Yeesh.