Yesterday, First Round Capital VC Jeff Kopelman posted to his blog what he thought was clear evidence that Yahoo employees are planning a mass exodus. Through his venture firm, he bought Facebook ads with the message "Leaving Yahoo?" in November and again this week after Microsoft announced its intentions to buy the company. Clickthrough rates on the ads were up 300 percent this time over last, Kopelman said. What Kopelman didn't say was that this time the ads included Facebook profile pictures of current Yahoo employees. The pictures appeared because the Yahoos had joined First Round Capital's Facebook group — not because they'd left the company.