I believe the vast majority of organizations honestly try to avoid over using software license. Even so, the nature of software licensing actually facilitates mistakes causing noncompliance. This post lists some useful tips for avoiding mistakes by improperly calculating Microsoft licenses in your environment.
Careful when deploying a version or edition that is different from the license purchased: This can be a tricky move. Downgrading the version is generally (but not always) straight forward but not so with editions. This is a very common mistake.
Understand the effect of the sales channel on the licensing rules: There is a big difference between OEM, Volume and Volume + Software Assurance (SA).
Use the proper set of use rights: Usage rights are simply the rights offered by the publisher to the purchaser. Many variables affect the usage rights such as product, version, edition and sales channel. The usage rights can restrict the use of the software in many ways such as number of users, transfer of the software to another system, number of processors, upgrade, downgrade, number of installations etc.
Be aware of the complexities caused by virtualization: License complexity is compounded dramatically by virtualization. Licensing rules are still being adjusted by publishers to cater for virtualization. I recently posted an article that referenced a virtualization licensing expert that recommended thoroughly analyzing the licensing affect prior to implementing virtualization…the change in licensing cost may be a “show stopper”.
Ensure a licensing expert available: As you can see, licensing can be tricky business. These days it really requires the resources of a dedicated team of people to properly protect an organization from being exposed to risk.
For more information on this topic see Versions, Editions and Downgrades Key to Microsoft Licensing by Rob Horwitz of Directions on Microsoft posted on The ITAM Review.