Using search engines to do your job for you
Search engines can produce an absolute overload of information if not used efficiently. Not only can you find information about the financials of your targets, but also information about key employees, usernames and passwords, confidential documents such as network diagrams, information indicating what types of software or hardware you use or have in place, and even if systems are in a default state. This information can be devastating in the wrong hands. As a penetration tester your focus should be to bring this type of information forth and show the clients how it can be used to gain access to the clients' most critical assets (and hopefully, you will tell them how to fix the problem as well!).
Tip
There are search engines that cache information for quick access, and there are search engines that will archive sites and documents for years on end. There are even search engines that focus strictly on networking equipment such as wireless access points...