There's this enormous focus on 'web scale' technologies. This focus necessarily invokes visualizing and making sense of terabytes and eventually even petabytes of data; conventional approaches would take thousands or millions of man hours to accomplish the same level of analysis that computers can perform in hours or days.

Tom Mitchell's definition of machine learning algorithms as those that improve their performance at some task with experience is precisely the way in which humans go about learning what's necessary to perform the same tasks that formerly took thousands or millions of hours.

For highly dimensional problems, such as text classification (i.e., spam detection) or image classification (i.e., facial detection), it's almost impossible to hard code an algorithm to accomplish its goal without using machine learning. It's much easier to use a binary spam/not spam or face/not face labeling system that, given the attributes of the example, can learn which attributes beget that specific label. In other words, it's much easier for a learning system to determine what variables are important in the ultimate classification than trying to model the "true" function that gives rise to the labeling.