Reusing the existing Standard Objects

When designing your object model, a good knowledge of the existing Standard Objects and their features is the key to knowing when and when not to reference them. Keep in mind the following points when considering the use of Standard Objects:

• From a data storage perspective: Ignoring Standard Objects creates a potential data duplication and integration effort for your end users if they are already using similar Standard Objects as pre-existing Salesforce customers. Remember that adding additional custom fields to the Standard Objects via your package will not increase the data storage consumption for those objects.
• From a license cost perspective: Conversely, referencing some Standard Objects might cause additional license costs for your users, since not all are available to the users without additional licenses from Salesforce. Make sure that you understand the differences between Salesforce (CRM) and Salesforce Platform licenses with respect to the Standard Objects available. Currently, the Salesforce Platform license provides Accounts and Contacts; however, to use Opportunity or Product objects, a Salesforce (CRM) license is needed by the user. Refer to the Salesforce documentation for the latest details on these.

Use your user personas to define what Standard Objects your users use and reference them via lookups, Apex code, and Visualforce accordingly. You may wish to use extension packages and/or dynamic Apex and SOQL to make these kind of references optional. Since Developer Edition orgs have all these licenses and objects available (although in a limited quantity), make sure you review your package dependencies before clicking on the Upload button each time to check for unintentional references.