LONDON, Oct 10 (Reuters) - Fans will be able to sell unwanted tickets online during the 2014 World Cup in Brazil as FIFA tries to ensure that as many seats as possible are filled at stadiums. The London Olympics and Euro 2012 were both blighted by rows of empty seats at supposedly sold-out venues, frustrating fans and detracting from the spectacle for television audiences. Sponsors will also be asked to give details of who is using their tickets, FIFA Marketing Director Thierry Weil said on Wednesday, adding that it was impossible to eradicate "no shows" from ticket holders. ... More...