Referencing both a node and user in the same field In Drupal 7, I am looking to create a field in a content type that can either reference another specific content type and/or also reference a user.  I am creating the content type programmatically in the .install file and am looking to be able to reference both types in the same field.  

It currently works with one or the other as:

  'field_sport_team_members' =&gt; array(
    'field_name' =&gt; 'field_sport_team_members',
    'label' =&gt; 'Team Members',
    'cardinality' =&gt; FIELD_CARDINALITY_UNLIMITED,
    'type' =&gt; 'node_reference',
    'description' =&gt; 'The members of the team',
    'weight' =&gt; '3.5',
    'required' =&gt; 0,
    'settings' =&gt; array(
      'referenceable_types' =&gt; array('club_person'),
    ),
  ),


for the reference to the content type and

'field_club_person_user' =&gt; array(
  'field_name' =&gt; 'field_sport_team_members',
  'type' =&gt; 'user_reference',
  'label' =&gt; 'Team Members',
  'description' =&gt; 'If this entry corresponds to a user, you can select the user here.',
  'weight' =&gt; '3',
  'cardinality' =&gt; FIELD_CARDINALITY_UNLIMITED,
  'translatable' =&gt; TRUE,
  'locked' =&gt; FALSE,
  'settings' =&gt; array(
  'referenceable_roles'  =&gt; array (
    4 =&gt; '4', //captain
    5 =&gt; '5', //player
   ),
   'referenceable_status' =&gt; array(
     1 =&gt; '1',
     0 =&gt; 0,
    ),
   ),
  ),


for the reference to the user type.

I guess my real question is now with the advent of "entities", is it possible to make a entity reference, but also to specify which content types to search for as well?
There are a few ways to do this. You said "and/or", you could use Field Collection and add a node reference and a user reference to it. See the field collection module. 

The other option would be the relation module or the entity reference module which can both reference any "entity." The former is a lot more complex. Entity reference has a usable widget with autocomplete which might be exactly what you need. To narrow the entity reference down to the exact content types you want along with users, you will probably have to write a custom widget. You can see the default widget implementation in the source.