It's easy to wind up in that spot, irritating all the same though. I try to use everything I do with clean degradation with ad-block, etc... only local and/or cdnjs scripts required (if anything).
Me too. I develop with umatrix enabled, with font loading disabled, so that I can catch these problems, etc.
Forces you to use sensible technology, like svg and not fonts for icons, and catch these types of missing optional dependency errors, and not depend too much on a specific font in your design, so that if brwser forces something else, you don't start having overflowing text everywhere.
http://tinypic.com/view.php?pic=2v31s94&s=9#.W_KD0idx2Rs