Guys, there are MANY reasons why you may see artifacting on video playback in dark scenes.
The "black crushing" example only really applies to OLED screens (GS3, Note II, etc..) when the screen is unable to display the last few darkest shades of grey and just cuts into black.
The macroblocking in dark scenes is, typically, a compression tradeoff to allow for smaller file sizes. If a 1 hour video in 720P is under 2GB in size, you WILL have this happen. This is how H264 / MP4 compression works.
You may not notice this as much on a smaller phone screen, or a lower resolution screen, or even on a lower quality display. Play that same clip on a 24" monitor and it will look much uglier than it did on your 5" phone.
To truly compare, you have to play the same file on multiple devices / displays at the same time. Try this with a highly compressed file and then with a higher bitrate file.