By disabling tracking cookies, you may not be allowed certain functions of the website you are surfing. On top of that cookies are also used to track and configure your personal preferences on a certain sites. overall no major disruptions but still there will be some inconveniences.
Most major tracking cookies used include site visitor trackers such as statcounter and google analytics to track how many hits, from where how you click the link. If i'm not wrong, Yahoo also embeds cookie to remember usernames and password stores9correctme if i'm wrong).