Using Django trunk with the python-memcache background, I can set the cache, but not get from it. But it's definitely setting, because you can see that the underlying memcache instance (cache._cache) is able to get -- it's just django's cache.get() method

Cache settings

CACHES = {
  'default': {
    'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
    'LOCATION': '127.0.0.1:11211',
    'KEY_PREFIX': 'barstar_',
  }
}

F'd up memcaching with Django.

>>> from django.core.cache import cache
>>> cache.clear()
>>> cache.get('testing_yo')
>>> cache.set('testing_yo', 'testing, yo!', 300)
>>> cache.key_prefix
'barstar_'
>>> 
>>> # Using Django's cache framework's get method
>>> cache.get('testing_yo')
>>> cache.get('%stesting_yo' % cache.key_prefix)
>>> 
>>> # Using the underlying memcached instance
>>> cache._cache.get('testing_yo')
'testing, yo!'
>>> cache._cache.get('%stesting_yo' % cache.key_prefix)
>>> 

For good measure, without the KEY_PREFIX in the settings:

>>> from django.core.cache import cache
>>> cache.clear()
>>> cache.get('testing_yo')
>>> cache.set('testing_yo', 'testing, yo!', 300)
>>> cache.key_prefix
''
>>> 
>>> # Using Django's cache framework's get method - THIS IS THE REAL ISSUE
>>> cache.get('testing_yo')
>>> 
>>> # Using the underlying memcached instance - THIS IS JUST HERE TO GIVE MORE INFO
>>> cache._cache.get('testing_yo')
'testing, yo!'
>>> cache._cache.get('%stesting_yo' % cache.key_prefix)
'testing, yo!'
>>> cache._cache.get('%s:1:testing_yo' % cache.key_prefix)

When I switch to the locmem backend, it works fine:

>>> from django.core.cache import cache
>>> cache.clear()
>>> cache.get('testing_yo')
>>> cache.set('testing_yo', 'testing, yo!', 300)
>>> cache.key_prefix
''
>>> 
>>> # Using Django's cache framework's get method - THIS IS THE REAL ISSUE
>>> cache.get('testing_yo')
'testing, yo!'
>>> 
>>> # Using the underlying memcached instance - THIS IS JUST HERE TO GIVE MORE INFO
>>> cache._cache.get('testing_yo')
>>> cache._cache.get('%stesting_yo' % cache.key_prefix)
>>> cache._cache.get('%s:1:testing_yo' % cache.key_prefix)
"S'testing, yo!'\np1\n."
>>>