Since ma.MaskedArray inherits from ndarray, all ndarray methods are inherited, but with exception of ufuncs, such inheritance is ill-advised and may lead to silent data corruption:

>>> x = ma.masked_all(5)
>>> x.item(0)
-1.2882297539194267e-231

The list of such methods includes:

1. choose
2. dumps
3. dump
4. item
5. partition
6. argpartition
7. fill
8. searchsorted
9. dot

I would classify this issue as a bug, but a fix can be as simple as making these methods raise NotImplementedError.