Refering to the title, I think entity reference is potential and support reference not only to taxonomy but also others e.g. users, comment, content, etc.: http://drupal.org/project/entityreference. It is good to have support for entity reference, just imho.

Comments

Title:Support for Entity referenceMicrodata support
Project:Microdata» Entity reference

Yeah, it's a top-10 field type defining module, so I agree. It shouldn't be hard to support, either.

I'm going to move this to the Entity Reference queue, and I have also listed the issue in the table of field formatter support issues.

Title:Microdata supportMicrodata support for Entity Reference

...following. A less vague title for our dashboards ;)

Can anyone describe what needs to happen?

I expect to have a student for GSOC who could take a look at what needs to happen for this field. If you like, you can postpone the issue until then.

There are several usecases this should solve (please correct or add to this)

Taking Recipe as an example.
http://schema.org/Recipe

Basic usecase:
A Recipe node may entityreference several ingredient nodes.
The recipe node page should output the ingredient node names as Microdata ingredients.

Advanced usecase:
A Recipe has nutritional information (outputted as Microdata and/or as information presented to the user)
http://schema.org/NutritionInformation
The ingredients (ingredient nodes) have nutritionalinformation.
The nutritional information from the Recipe can be calculated by looking at the nutritionalinformation of the ingredients and the amount used of those ingredients.