Archetypes & Baby-Face Bias:

The Remember the Milk logo is comprised of an image and text that both appear to be hand-drawn, almost as if they were created by a child. The logo uses the baby face bias (the cow head) combined with the hand-written text to appeal to the archetype of child made drawings.

In practice, these principles make users of Remember the Milk perceive the RTM brand as being honest and innocent. In turn, these perceptions would impact the way the users feel about the functions of tool the itself - IE: they might be forgiving about small application glitches and bugs.