This trended July 29, 2010 because...
Fans of Justin Bieber routinely panic when he is no longer trending, and jump to the conclusion that Twitter has banned his name from trending topics. Fans used the Bustin Jieber tag to attempt to bypass this supposed ban, and now the Brazilian "beliebers" invented the Bustin Drew Jieber tag.
Related links
Twitter Search for BUSTIN DREW JIEBER
History
First seen
July 29, 2010