insufficiant mating material

At some point in his life any given developer will encounter an issue where they must make a choice between practicality, and theoretical purity.
Arguments exist on both sides which choice God made.

There is another side to this rule. See this game:

http://en.lichess.org/bye820e7

By FIDE rules, this should be a draw, as neither side can move his pawns, and the kings can't cross the center, so no sequence of moves ends with white being mated.

Under lichess rules, however, it is 0-1, since black has 3 pawns.

This situation is probably more common than the one in #1