Ben Callahan at Sparkbox draws an analogy between the Matrix's concept of "there is no spoon" to "there is no breakpoint" — it all depends the content. Callahan also suggests using ems instead of pixels in media queries.
In a recent Smashing Magazine article, "Logical Breakpoints for Your Responsive Design", Vasilis van Gemert emphasizes that "common" screen sizes no longer exist and suggests configuring breakpoints using readabilty theory.
Here are two heuristics cited by van Gemert that can be helpful as we move from pixel-perfect breakpoints to content-influenced breakpoints:
- “Anything from 45 to 75 characters is widely regarded as a satisfactory length of line for a single-column page set in a serifed text face in a text size.” — Robert Bringhurst The Elements of Typographic Style
- “A column is easy to read if it’s wide enough to accommodate an average of 10 words per line.” — Josef Müller-Brockmann Grid System in Graphic Design
Author van Gemert suggests that web designers start with a small screen layout and configure a break each time the "width of the main content grows wider than either 75 characters or 10 words".
Responsive design has moved beyond the pixel — it's all about the content!