The Resources folder is a common source of many problems in Unity projects. Improper use of the Resources folder can bloat the size of a project’s build, lead to uncontrollable excessive memory utilization, and significantly increase application startup times.
These problems are described in detail in the Best Practice Guide AssetBundles and Resources. In particular, refer to the Resources chapter for more information on the above problems.
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.