You cannot share the same feed
items across multiple feeds. However, you can use one single master feed with all of the feed items for a particular
placeholder type. In fact, we encourage this to keep things manageable and to limit the number of feed objects in your account (you can only have
20 per account).
For example, you could have a single
Feed for sitelinks containing all of the
FeedItems for all of your sitelinks across all of your campaigns and ad groups. You would then control which
FeedItems served under each campaign or ad group using the
matchingFunction on your
CampaignFeed and/or
AdGroupFeed objects for each campaign and/or ad group.