Large Objects

I need to do some investigation into the way Postgres handles large
objects for a major project involving large objects.  My questions are:
    * Can large objects be stored within a field value or must they be
referenced by OID?
    * Are large objects backed up in the normal way or does special
action have to be taken?
    * If the objects are restored or migrated will they retain their OID?
    * If not, is there another means of referencing them that would be
persistent through migrations?
    * Is it practical/desirable to store files MIME-Encoded inside a
text field?
       * The obvious advantages:
          * definitely portable across migrations and backups
          * based on universal technology
          * easy to code
          * easy to reference and version-control
       * The obvious disadvantages:
          * slow, Slow, SLOW
          * significant increase in per-file storage requirements

Any help would be greatly appreciated.  Hope I'm posting to the right
list.

Dan