[tptacek]

Because you're worried about attackers constructing four thousand rainbow tables?

[wizardishungry]

You wouldn't need 4096 if the choice of the salt was non-random; some versions of Unix used the first 2 characters of the username. What's the space requirement for a single rainbow table?

[tptacek]

I don't know, but none of what they did was even marginally useful against iterated password crackers, so, change your password.