DES: Q about SparseDataFrame._combine_match_columns behavior
There is some idiosyncratic behavior that I think is non-intentional, need to double check: cc @jreback introduced the relevant code 8ee0a898a74df38318dfd01b6f9faa7957b0543c

SparseDataFrame._combine_match_index and SparseDataFrame._combine_match_columns are both for arithmetic ops with a Series object, but with different alignment treatment.  When calling the constructor, combine_match_index passes `default_fill_value = self._get_op_result_fill_value(other, func)`, which matches `_combine_frame` behavior.  _combine_match_columns just passes `default_fill_value = self.default_fill_value`.

I think that `_get_op_result_fill_value` should be called in both cases.  Can anyone confirm?

(BTW this is relevant even though the class is deprecated because consolidating the behavior will allow us to streamline code in ops)
