Do not search the visibility offered by Google is a big mistake. You would spend close to many opportunities. But another mistake would be to focus only on the giant Mountain View: indeed, neglecting the other engines is not a good thing. The contribution of potential traffic could be significant.

And one last thing: do not focus all your efforts on SEO. Much you can win big, as you may lose everything! Imagine if Google penalizes your site or downgrades following the arrival of a new animal black and white: you would have more Internet traffic, and your business plan is likely to collapse. This does not happen to others, there are many examples, and many are still those who were not aware that this sword of Damocles over their head ...