Just keep in mind that Google uses extensions with the robots.txt file that are not valid with many other spiders, such as the Allow directive and the use of an asterisk wildcard (*) with a directive's arguments. These are not part of the official standard for the robots.txt file.
You should set up a Google section in robots.txt if you want to use the Google extensions. If you set up a Google section, Google will not recognize other spider directives on the page, so you need to repeat every area in your site that you do not want Google to index.
Examples. The first example (from the Google page) is actually incorrect because not all spiders recognize the Allow directive. Yahoo recognizes it, but it looks like Bing does not. This is a good example of Google viewing the Internet through a mirror.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin