Storing the virtualenv directory inside git will, as you noted, allow you to deploy the whole app by just doing a git clone (plus installing and configuring Apache/mod_wsgi). One potentially significant issue with this approach is that on Linux the full path gets hard-coded in the venv's activate, django-admin.py, easy_install, and pip scripts. This means your virtualenv won't entirely work if you want to use a different path, perhaps to run multiple virtual hosts on the same server. I think the website may actually work with the paths wrong in those files, but you would have problems the next time you tried to run pip.
The solution, already given, is to store enough information in git so that during the deploy you can create the virtualenv and do the necessary pip installs. Typically people run pip freeze to get the list then store it in a file named requirements.txt. It can be loaded with pip install -r requirements.txt. RyanBrady already showed how you can string the deploy statements in a single line:
# before 15.1.0
virtualenv --no-site-packages --distribute .env &&\
source .env/bin/activate &&\
pip install -r requirements.txt
# after deprecation of some arguments in 15.1.0
virtualenv .env && source .env/bin/activate && pip install -r requirements.txt
Personally, I just put these in a shell script that I run after doing the git clone or git pull.
Storing the virtualenv directory also makes it a bit trickier to handle pip upgrades, as you'll have to manually add/remove and commit the files resulting from the upgrade. With a requirements.txt file, you just change the appropriate lines in requirements.txt and re-run pip install -r requirements.txt. As already noted, this also reduces "commit spam".