An employment policy will vary depending on the needs of the business. After all, a business may not want or need to provide job postings for every position. Such a policy could slow down the business. On the other hand, a business which has had a couple of disappointments could decide that a more stringent policy could provide better results.
Hiring and termination are areas where there is a lot of inherent risk. These are key components of running a business. In making these decisions, there are a lot of pitfalls to be dealt with and most of these risks and pitfalls are in the creation of the team. However, there is legal risk as well.
The tendency is for people who are not hired just mutter disappointed or angry things to themselves. There is not necessarily any action taken beyond that. However, both hiring is subject to the same laws and regulations as terminations which can be challenged in a court of law. Such legal action tends to be taken for terminations, unless they are done carefully.
A strong policy can remove a lot of this risk. A hiring process lays our the groundwork for finding an individual who has the potential to fit into the organization. A termination policy provides notice to the employee over what kind of actions will result in being fired. This allows for consistency and answers the questions which opened this post. Keep in mind that no policy will be perfect and there is a need to manipulate the policy as the company grows and changes.