Justin Bieber was famously discovered on YouTube, perhaps the most spectacular example to date of an entertainer parlaying the internet into mainstream popularity — now, a startup headed by a music industry veteran wants to repeat that success using Twitter as a backbone. Lyor Cohen, who cut his teeth at Rush and Def Jam in the 80s and 90s before heading Warner Music Group in the last decade, announced at French music conference Midem this weekend that his new company 300 is working with Twitter to mine millions of tweets in the hopes of finding the next platinum-selling artist. Twitter gets something out of the deal, too At its founding last year, Cohen and his team described 300 as a content company primed to help artists make their mark — in the age of Twitter, Pinterest, and Vevo, the old notion of a record label doesnt quite cover it.