I have spent many years on the technical side of the printing industry especially in imaging for Newspapers and Magazines.
Most of what the guy in the video is saying has a ring of truth but he does tend to fall into his own trap of not knowing exactly what his is talking about.
The most common error is folk confuse image (photo) resolution with printer (imager) resolution. Current imager technology scans the press printing plate directly with a laser.
Newspapers require fast imaging so the resolutions are typically 1016 dpi or 1200 dpi. Newsprint is a low quality paper and the print quality is determined by the smallest area of ink that will stay stuck to the paper as it whizzes through the press.
Glossy Magazines require quality and often use resolutions of up to 3600 dpi. In this case the paper and press used can print very much finer dots.
Newspapers will print photos using standard half-tone in the range of 85 - 100 lpi dependent of their press ( note lpi - lines per inch used but often you will also hear dpi used for the same term).
Glossy Magazine will print photo using standard halftone in the range of 120 - 185 lpi. Standard half-tone is where you see the picture made up from halftone dots. Each halftone dot is made up from a cluster of imager dots.
OK that's a bit of background info.
Lets get back to the question Does DPI really matter ?
Well the simple answer is it depends on what you are printing to as to what DPI should be used.
In the case of half-tone printing I am afraid strictly speaking the 2 times sampling theorem rule still apply to avoid quality issues such as moire patterning. so for 150 lpi you require 300 dpi or 85 lpi you require 170 dpi.
Halfway down the page on the link shows a brick wall with and without moire patterning.
http://en.wikipedia.org/wiki/Nyquist...mpling_theorem
There are other screening technologies such as stochastic which are said to required lower dpi requirements but rarely used in the real world.
Inkjet printers use various dithering techniques to produce a continuous tone effect so that no dots are seen. Good results are seen using 150 dpi.
The limit of the human vision system is said to be 7 line per mm which equates to 180 dpi or a half-tone of 180 lpi. So no point in going beyond that as the improvement will not be seen without a magnifying glass.