When exporting tab-delimited data from a DataForm, only the field names and values are exported.  None of the "extra" information about the entry (such as entryId, username, submissionDate) are exported. 

I am filing this as a bug report rather than a feature request because in reviewing the code (DataForm::www_exportTab), it appears that this extra info was meant to be exported, as it is gathered into the data array here:

        while (my $entryData = $entries->hashRef) {
                $data[$i] = {
                        entryId => $entryData->{DataForm_entryId},
                        ipAddress => $entryData->{ipAddress},
                        username => $entryData->{username},
                        userId => $entryData->{userId},
                        submissionDate => $self->session->datetime->epochToHuman($entryData->{submissionDate}),
                        };

However, later when the actual text to export is created, only fields from the DataForm_field table are pulled out, so the fields defined above do not get exported:

                foreach my $fieldId (keys %fields) {
                        next if (isIn($fields{$fieldId}, qw(to from cc bcc subject)) && $noMailData);
                        my $value = $record->{$fields{$fieldId}};
                        $value =~ s/\t/\\t/g;
                        $value =~ s/\r//g;
                        $value =~ s/\n/;/g;
                        push(@row, $value);
                }
                $tab .= join("\t", @row)."\n";

 Where %fields is defined above as:

        my %fields = $self->session->db->buildHash("select DataForm_fieldId,name from DataForm_field where
                assetId=".$self->session->db->quote($self->getId)." order by sequenceNumber");