COPY fails on 8.1 with invalid byte sequences in text types

You can insert invalid UTF8 bytes sequences into a TEXT type on an 8.1
installation by doing something like:

INSERT INTO foo(t) VALUES('\xFF');

Then, you can do a:

COPY foo TO '/some/file';

but if you try to do a:

COPY foo FROM '/some/file';

That will fail because /some/file contains invalid UTF8 sequences, even
though it's the same file you copied out.

It seems to be essentially a data corruption issue if applications
insert binary data in text fields using escape sequences. Shouldn't
PostgreSQL reject an invalid UTF8 sequence in any text type?

Regards,
    Jeff Davis