The problem comes into play when you try to select the actual LOB locator remotely, however straight INSERTs aren't a problem.

Code:
SQL> desc test_clob1
 Name                                      Null?    Type
 ----------------------------------------- -------- -----------------------
 A1                                                 NUMBER
 A2                                                 CLOB


SQL> desc test_clob2@remotedb
 Name                                      Null?    Type
 ----------------------------------------- -------- -----------------------
 A1                                                 NUMBER
 A2                                                 CLOB


SQL> declare
  2     big_text varchar2(32767) := rpad('#',32767,'#');
  3  begin
  4       insert into test_clob1 values (1, big_text );
  5  end;
  6  /

PL/SQL procedure successfully completed.

SQL> select a1, dbms_lob.getlength(a2) from test_clob1;

        A1 DBMS_LOB.GETLENGTH(A2)
---------- ----------------------
         1                  32767

SQL> select count(*) from test_clob2@remotedb;

  COUNT(*)
----------
         0

SQL> insert into test_clob2@remotedb
  2  select * from test_clob1;

1 row created.

SQL> select a1, dbms_lob.getlength(a2) from test_clob2@remotedb;
select a1, dbms_lob.getlength(a2) from test_clob2@remotedb
                              *
ERROR at line 1:
ORA-22992: cannot use LOB locators selected from remote tables


SQL> commit;

Commit complete.
However, if I do a COMMIT and then go to the remote database and do the same query, I get the following:

Code:
SQL> select a1, dbms_lob.getlength(a2) from test_clob2;

        A1 DBMS_LOB.GETLENGTH(A2)
---------- ----------------------
         1                  32767