While 75% of the population supports the protests after the first week, this is done for different reasons:The youngsters relying on non-partisan, occupy-movement inspired protests, find their voice over Anonymous. This approach is criticized by many who view this as over idealistic and without focus and those supporting it risks to be named "coxinhas" (newbies).
In the opposite of the spectrum you find more experienced protesters, mostly from the left wing movements, supporting a place for political parties - mainly PT (labour party, currently in power at the federal government) - at the protests. Their power comes from the protests in the 90s and they fear a nationalist movement leading to a right wing coup d'Etat.
Even if some of those supporting the protests are targeting the president Dilma Rousseff, the ordinary citizen prefers to target the national congress. With a number of scandals and poorly chosen representatives the congress has been the subject of growing insatisfaction since the mensalão (and even before).
To complete this equation, the governors of the biggest States in Brazil: São Paulo, Rio de Janeiro and Minas Gerais are leaders of the opposition holding big expectations that the World Cup 2014 will give them an important chance to beat the re-election of president Dilma or to be re-elected as governors in the elections next year. That said, accusations of mismanagement in the construction of the stadiums were not doing them a favor.