I'm perplexed by the fact that Google Analytics cannot track visitors to websites that have disabled first-party cookies and/or java script on their browsers. Are there any figures on how many visitors may do this at any one time? Obviously this is an element of a browser that a user would actually have to put effort forth to manipulate so it doesn't seem that it could be that widespread. It does make sense though that the greater the amount of traffic coming to a site, the greater the likely hood that the data could be skewed based on people's java being disabled.
The workaround for this factor is tracking users with the mobile version of the code. The drawback here is that you don't get the same tracking accuracy with things like location or aspects of a visitors presence on your site.