Heh in Programmer/"Commissioner" humor, it's those edge cases that killed me this year. I made some brutally dirty "proto-apps" that did certain things. But they don't work on DC. Or on any of 570 other sites. Oops.
I think Programming in general is like this, hence the current struggle to "micro monetize" and the people building "deep resources for free" just because no one needs to write the same crucial 10,000 line of code EVERY SINGLE TIME.