Navigated to a Forbes article recently and was about to exit since their Ad-wall detects uBlock when I noticed that the usual message had changed: https://i.imgur.com/fHawyXE.png
Logging in with a Google account did permit me to access the page [1]. Logging out and navigating back to the page brought up the "Sign in" prompt most of the time.
[1] http://www.forbes.com/sites/briansolomon/2015/09/02/father-and-son-become-billionaires-with-tanium-the-worlds-hottest-cybersecurity-startup/