It’s one thing to block cookies because you don’t want to be tracked, but in most cases cookies provide essential functionality for some sites, like sites using a logon via another third party site, like OpenID.
Trying to logon with your Google account to the Kinja network of sites for example doesn’t work if you’re blocking third party cookies in Chrome. The logon fails silently. To work around this (and presumably for other similar sites too), just add a ‘Cookie and site data exception’ in your Chrome settings, in this case for [*.]kinja.com