80 characters seems like such an arbitrary restriction. Once upon a time we were limited to 80 characters but we were also limited to monochrome ASCII text. Just as syntax highlighting improves readability, I think the occasional use of longer lines where appropriate improves readability - the shape of the code gives your eye additional clues about where you are in a section of code, allows you to have more lines on the screen at once, find what you're looking for faster, and isolates details that aren't crucial in getting the big picture. E.g. - inline lambdas or anonymous functions, strings, etc.

When I work on a codebase with formatting standards I try to follow them. This is 2013, though, and when I work on my own stuff I format it to get the most readability on my Macbook or 32" 1080p desktop screen, not a VT100 from 1987.