Maschwitz's Law is an admonition to camera manufacturers to enable the maximum feature set supported by their hardware, lest their users do it for them.
Or, put simply:
It’s no longer OK for cameras not to give us everything they’ve got. If they don't, we’ll just take it anyway.
First appearance here, where I wrote:
What I love about the new generation of cameras, such as those from Blackmagic, Red, and even GoPro, is that they all give you everything they’ve got. They’ll give you the highest image quality they can, in the smallest package possible. They’ll compress images as much or as little as you want. They’ll max out their resolution at the expense of frame rate, or vise versa—whichever you like. And they’ll pack their best dynamic range into any format they can record.
Examples of users "taking" functionality from cameras that had artificially held it back include Magic Lantern hacking raw video out of the 5D Mark III, and Cinematographer Paul Ream hacking his Sony F5 to enabled internal 4K recording.