This is what I actually got from 8.0.6 test database, which has very little activities in there though.

SQL> select bytes, maxbytes,maxblocks from dba_data_files;

BYTES MAXBYTES MAXBLOCKS
---------- ---------- ----------
57671680 0 0
235929600 0 0
199229440 0 0
36700160 0 0
115343360 0 0
5242880 0 0
6291456 0 0

7 rows selected.

SQL> select bytes from v$datafile;

BYTES
----------
57671680
235929600
199229440
36700160
115343360
5242880
6291456

So why all the zeros for maxbytes and maxblocks?