CBS, ABC, and NBC representatives tell TMZ that Fallon's successful ratings have given the network the impression that they hold extreme bargaining power.
Apparently NBC has given word to celebrities, agents and publicists that guests who wish to be on The Tonight Show cannot make appearances on other networks. The ultimatum includes morning shows and other late night talk shows, but not other NBC programs like Today and Dateline.
Sources from ABC's Good Morning America say they've already experienced fallout with potential guests.
Celebrity Families of 2014 [PHOTOS]