Multiplying Together Series with MultiIndexes
I have a question regarding multiplying two Series that have MultiIndexes. In pandas, I can multiply these two Series and it makes sense:

``` python
>>> iterables = [
    ['A', 'B'],
    ['foo', 'bar', 'baz', 'qux'],
    ['one', 'two', 'three']
]
>>> s1 = pd.Series(range(12), index=pd.MultiIndex.from_product(iterables[1:3], 
                               names=['first', 'second']))
>>> s1
first  second
foo    one        0
       two        1
       three      2
bar    one        3
       two        4
       three      5
baz    one        6
       two        7
       three      8
qux    one        9
       two       10
       three     11
dtype: int64
>>> s2  = pd.Series(range(4), index=pd.MultiIndex.from_product([iterables[1]], 
                                        names=['first']))
>>> s2
first
foo      0
bar      1
baz      2
qux      3
dtype: int64
>>> s2 * s1
first  second
foo    one        0
       two        0
       three      0
bar    one        3
       two        4
       three      5
baz    one       12
       two       14
       three     16
qux    one       27
       two       30
       three     33
dtype: int64
```

I want to do the same thing with deeper MultiIndexes, but it raises an exception:

``` python
>>> s1 = pd.Series(range(24),index=pd.MultiIndex.from_product(iterables, 
                               names=['first', 'second', 'third']))
>>> s1
first  second  third
A      foo     one       0
               two       1
               three     2
       bar     one       3
               two       4
               three     5
       baz     one       6
               two       7
               three     8
       qux     one       9
               two      10
               three    11
B      foo     one      12
               two      13
               three    14
       bar     one      15
               two      16
               three    17
       baz     one      18
               two      19
               three    20
       qux     one      21
               two      22
               three    23
dtype: int64
>>> s2 = pd.Series(range(8),index=pd.MultiIndex.from_product(iterables[:2], 
                                names=['first', 'second']))
>>> s2
first  second
A      foo       0
       bar       1
       baz       2
       qux       3
B      foo       4
       bar       5
       baz       6
       qux       7
dtype: int64
>>> s2 * s1 # raises an exception
```

Shouldn't I be able to multiply these two Series together without raising an exception? Am I doing something wrong?
