I was suprised the the other day by a SciPy-linking issue:

$ python -c 'import scipy.linalg'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/scipy/linalg/__init__.py", line 9, in <module>
    from basic import *
  File "/usr/lib/python2.7/site-packages/scipy/linalg/basic.py", line 14, in <module>
    from lapack import get_lapack_funcs
  File "/usr/lib/python2.7/site-packages/scipy/linalg/lapack.py", line 15, in <module>
    from scipy.linalg import clapack
ImportError: /usr/lib/python2.7/site-packages/scipy/linalg/clapack.so: undefined symbol: clapack_sgesv

Searching around, it turns out there have been problems like this for a while, and it's flared up again recently. There's a new Gentoo bug tracking the most recent issues. In general, NumPy/SciPy seems to be picky about the particular BLAS implementation you're using, and you'll get problems like the above if you're using the reference implementations of BLAS and LAPACK.

$ for x in blas cblas lapack; do eselect $x list; done
Installed BLAS for library directory lib
  [1]   reference *
Installed CBLAS for library directory lib
  [1]   gsl
  [2]   reference *
Installed LAPACK for library directory lib
  [1]   reference *

You can fix the problem by installing and selecting the ATLAS libraries

$ sudo emerge -av blas-atlas lapack-atlas
$ for x in blas cblas lapack; do sudo eselect $x set atlas; done

after which you should re-install any packages that may need to be relinked.

$ sudo emerge -av numpy scipy

Now you can import the linear algebra module without crashing:

$ python -c 'import scipy.linalg'