nothing is mentioned here on detecting the service status: http://code.google.com/appengine/docs/python/memcache/clientclass.html perhaps it's just a matter of catching the exception.
i have not been paying close enough attention to know how often there might be service disruptions, but none of my clients have complained that customers are having problems with the sites i work on. but do remember that memcache data can be evicted at any time for any reason, so you should have a fall-back plan.
