The hotline for the July 2 Hyde Park concert reported receiving 600 text messages per second Monday -- 3 million by the end of the first day tickets were available.
Organizers predict around 88 million requests will be received by the close of competition midnight June 12.
The winners of the 150,000 tickets will be picked at random from a database of entrants who correctly identify the G8 summit host city in a multiple-choice question.
The name Live 8 is a play on the G8 summit in Scotland July 6-8, when leaders of the world's eight richest nations gather to discuss British proposals to cancel African debt and double international aid.
Simultaneous concerts will held in Paris, Berlin, Rome and Philadelphia.