BUG: reindex strange behaviour
When I try to reindex a Series object I get a really weird result.

``` python
>>> s = pd.Series([1,2,3,4,5], index=['a', 'b', 'c', 'd', 'e'])
>>> s.reindex(['a', 'g', 'c', 'f'], method='ffill')
a     1
g     5
c   NaN
f     5
dtype: float64
```

According to the documentation I should have got something like:

``` python
a   1
g   1
c   3
f   3
dtype: float64
```

So either the documentation is not valid, or reindex is not working correctly or I haven't understood how this beast works?
