When news came out the other day that Flipboard just raised another $50 million at a $200 million valuation for its iPad news reading app, I gave CEO Mike McCue a hard time on Twitter and here on TechCrunch. Does an iPad app startup really need $50 million, or is this yet another sign of a bubble? McCue responded on Twitter, but yesterday we spoke by phone and he went into great detail about why exactly he thinks he needs $50 million. He came up with the number a few months ago. It's what he calculates he needs to get to cashflow positive, or at least pretty close (more on that below). Raising money is distraction, and his preference was to raise it all at once. But towards the end of our conversation, he also mentioned another concern which was a factor in taking as much money as he can right now. "I see a lot of competition down the pike," he says. Rumors have been reaching him that there is a team of engineers at Google who are "saying they are building a Flipboard killer." He adds quickly, " I have no idea what it is," but hearing about "this desire to kill us" is unsettling and it does add "a little concern about the unknown."