Well, that is the million dollar question, isn’t it? I have seen a lot of accusation and rumor going around, but I have yet to see any substantiating evidence.
In fact, updating twitters from LinkedIn are saying that they have not been able to substantiate this claim. Regardless, it would be a good idea to change your password. Their passwords are SHA-1 hashed, but that doesn’t mean they are impossible to crack. Yep, it will take time, unless this breach happened a long time ago – and they were just posted online.
If this pans out as a verifiable hack, then this would constitute a major security breach. And if that is the case, how long has it been?