I'm starting with Python 3, using Raspbian (from Debian), and using virtualenv.  I understand how to create/use a virtualenv to "sandbox" different Python project, HOWEVER I'm a bit unclear on whether one should be setting up a different linux user for each project (assuming that the project/virtualenv will be used to create & then run a daemon process on the linux box).  
So when creating separate python environments the question I think is should I be:

creating a new linux user account for each deamon/acript I'm working on, so that both the python virtual environment, and the python project code area can live under directories owned by this user?
perhaps just create one new non-administrator account at the beginning, and then just use this account for each project/virtual environmnet
create everything under the initial admin user I first log with for raspbian (e.g. "pi" user) - Assume NO for this option, but putting it in for completeness.
In the general case, there is no need to create a separate account just for a virtualenv.
There can be reasons to create a separate account, but they are distinct from, and to some extent anathema to, virtual environments. (If you have a dedicated account for a service, there is no need really to put it in a virtualenv -- you might want to if it has dependencies you want to be able to upgrade easily etc, but the account already provides a level of isolation similar to what a virtualenv provides within an account.)
Reasons to use a virtual environment:

Make it easy to run things with different requirements under the same account.
Make it easy to install things for yourself without any privileges.

Reasons to use a separate account:

Fine-grained access control to privileged resources.
Properly isolating the private resources of the account.
should new python virtualenv's be created with new linux user accounts?