Stupid nonlinear scales

Here is a list of stupid nonlinear scales

• f-numbers. Inverse square root of illuminance (for exposure calculations). I'd be okay with f-number squared if we measured shutter speeds in milliseconds. Then a shot that required 4 ms at f²/4 (1/250 at f/2) would require 8 ms at f²/8 (1/125 at f/2.8). 
• Megapixels. Square of resolution. For photography, I think we should use equivalent 35mm dpi:
  

  dpi at 24x36mm	Resolution	Megapixels
  1000	1400 x 950	1.3
  2000	2800 x 1900	5.4
  3000	4200 x 2800	12
  4000	5700 x 3800	21

  Megapixels are useful for signal processing and file size considerations, though.
• Miles per gallon. Reciprocal of fuel consumption. Gets even more exaggerated when you look at differences between mpg ratings. We should use gallons/100 miles.
  

  Vehicle	mpg	gal/100mi
  Old SUV	13	7.7
  New SUV	21	4.8
  TDI Jetta	36	2.8
  Prius	50	2.0
  Bicycle	∞	0.0

  These numbers are fabricated but not ludicrous. My point is that the mpg system makes high-efficiency vehicles look way better than they actually are. 
• Going from an old to new SUV is a 60% increase in "efficiency", whereas going from a new SUV to a Prius is a whopping 140%. And yet they have the same impact on fuel consumption, which is what we actually care about.
• Same goes for old vs. new SUV compared to Jetta vs. bicycle (though more recent data suggests that we underestimated the TDI fuel economy)

Here's just a few to start - I'm sure there's more out there, and I'll update this post as I come across them.