I'm guessing the GP was referring to the fact that Levison didn't update Lavabit to prefer ciphers that provide perfect forward security. Here is his own admission on the subject:-

" When I was designing the Lavabit encrypted storage feature in 2004, it simply wasn’t possible for an attacker to intercept and decipher a large number of SSL connections in real time. This assumption was presumed true even if an attacker managed to gain access to the SSL private key. The situation has obviously changed. Network tools now decipher SSL connections efficiently, and servers are fast enough to make this attack a reality. A theoretical weakness became practical. I missed that development. More importantly, I failed to update the Lavabit SSL configuration to prefer ciphers that provided perfect forward secrecy. "

Source: http://arstechnica.com/security/2013/11/op-ed-lavabits-found...