"Those who block all cookies, will not be tracked by Google Analytics, because all data is transmitted to the Google Analytics server via the basic (first party) cookie.

Those who delete cookies, will still be tracked, but they will be defined as new visitors every single time, because the web analytics system will not be able to associate them with their previous site visits."

While deleting or disabling cookies is helpful one needs to block web bugs as well.

The analytics services - there are many in addition to google - dont need cookies to associate your previous site visits because your IP, user agent, capabilities such as installed plugins, language and other stuff in the headers if your http GET or POST requests are enough to identify you.