I've seen lots of posts about how this isn't possible directly from InfoPath. Most solutions suggest saving the AccountID as text and then using a SPD workflow to set the Person/Group field in SharePoint.
Can anyone explain why/how this works if I create a SP list, add a Person/Group field and then Customize the list form with InfoPath? When I do this, the form automatically is created with the People Picker, and values are saved back into the SP list field - no problem. Is there something in InfoPath making this work, or is SharePoint doing something behind the scenes?