In order to create a virtual environment in a non-system (virtual) version of python under the control pyenv, you need to use a slightly different syntax. From the documentation of virtualenv plugin
$ pyenv virtualenv venv33
For me this only works if I am in the directory of the non-system version of python ~/.pyenv/versions/2.7.5. I have a tutorial that walks you through this at http://mofj.commons.gc.cuny.edu/2014/01/20/ubuntu-set-up-a-virtual-environment-with-ipython-numpy-and-pandas/