Understand the inherent risks of Google:
Internet searching is nowhere near perfection as of yet, and it only takes on itsy bitsy competing solution that is better than Google to bring the whole shit down. It will most probably come from some other garage firm.
The evolutionary problem with Google, is that they are not improving - just growing into other sectors, like Yahoo did. Google are not inventing anything new or doing improvements to their core searching functionality. Also, the advertising business is open to anyone...