Dynamic placeholders not showing in the Sitecore page editor

When working with an implementation of dynamic placeholders in Sitecore 8, I was not able to see my dynamic placeholders in the experience editor (aka page editor), yet I could use them by manually adding controls via the presentation details.

This was actually because of a setting in App_Config\Include\Sitecore.ExperienceEditor.config

WebEdit.PlaceholdersEditableWithoutSettings

Because the implementation of dynamic placeholders I was using at this time did not support placeholder settings, the config setting above (false by default) was stopping these placeholders from showing in page editor mode.

The fixes are to set this config setting to true (not recommended) or to find dynamic placeholders which support placeholder settings.