The v201111 version  of the DoubleClick for Publishers (DFP) API introduces SuggestedAdUnitService  which lets you get and approve those ad units that have tags on your web pages, but no corresponding ad units in DFP.  By default, only ad tags that have 10 or more requests will be returned as suggested ad units . They can be approved using performSuggestedAdUnitAction , after which they become ad units and you can manipulate them using InventoryService .  To use this service, please make sure you have a premium account  and that you have enabled the feature in the User Interface.Why Use Suggested Ad Units? 
ApproveSuggestedAdUnitsExample  from the client libraries  will show you how to do this.
Approving the suggested ad unit and targeting line items to it 
Promoting the page as featured content 
Recognize the user for quality content and auto-approve their pages 
 
Here's a Java code sample of how you would do this:// Set the number of requests to 50 or more.
Long NUMBER_OF_REQUESTS = 50L;
// Statement to fetch suggested ad units in descending order by number of 
// requests.
String statementText = "ORDER BY numRequests DESC LIMIT 500";
Statement filterStatement = 
    new StatementBuilder(statementText).toStatement();
SuggestedAdUnitPage page = new SuggestedAdUnitPage();
// List of suggested ad unit ids to approve.
List<String> suggestedAdUnitIds = new ArrayList<String>();
page = suggestedAdUnitService.getSuggestedAdUnitsByStatement(
    filterStatement);
if (page.getResults() != null) {
  for (SuggestedAdUnit suggestedAdUnit : page.getResults()) {
    if (suggestedAdUnit.getNumRequests() >= NUMBER_OF_REQUESTS) {
      // Add it to the ID list to be approved.
      suggestedAdUnitIds.add(suggestedAdUnit.getId());
      /*
       * Promoting the page as a featured content.
       * Recognize the user for quality content and auto-approve their 
       * pages.
       */
    }
  }
}
if (suggestedAdUnitIds.size() > 0) {
  // Modify statement to select suggested ad units from the list.
  filterStatement.setQuery(
      "WHERE id IN (" + StringUtils.join(suggestedAdUnitIds, ",") + ")");
  // Create action to approve suggested ad units.
  ApproveSuggestedAdUnit action = new ApproveSuggestedAdUnit();
  // Perform the action.
  UpdateResult result = suggestedAdUnitService.performSuggestedAdUnitAction(
      action, filterStatement);
}
 
These are just some of the things we think suggested ad units can be used for; we'd love to hear your ideas on our forum  or at an Office Hours Hangout.
Jeffrey Sham , DFP API Team