Google describes their doodles as "the fun, surprising and sometimes spontaneous changes that are made to the Google logo to celebrate holidays, anniversaries and the lives of famous artists, pioneers and scientists."
In 2000, Google produced its first doodle for Bastille Day. It was so well received by our users that doodles started showing up more and more regularly on the Google homepage. In the beginning, the doodles mostly celebrated familiar holidays; nowadays, they highlight a wide array of events and anniversaries from the Birthday of John James Audubon to the Ice Cream Sundae.
Over time, the demand for doodles has risen in the US and internationally. Creating doodles is now the responsibility of a team of talented illustrators and engineers. For them, creating doodles has become a group effort to enliven the Google homepage and bring smiles to the faces of Google users around the world. The index of doodles is available here, but please come back to finish reading this post.
Here is the complete doodle for Feb 14, 2012 in case you missed it.
And that is all Google wants. It doesn't want to control us or manipulate us but rather to make us happier by finding us what we truly want.
In return, that alone will make Google happier. And more profitable. I think it believes this to its core.