CCP Nozh has posted a developer blog detailing the rebalancing of speed in EVE Online . After a lengthy meeting in which the issue of speed was discussed, the devs laid down five basic tenets:

Speed must never reach ludicrous speed, which is defined as speeds where missiles and drones don't intercept the class of ship they were intended for.

There should be a significant and meaningful difference in speed between the ship classes.

Speed should not permit a larger ship to perform the role that a smaller specialized ship was intended for.

Afterburners should be a viable module selection for PVP.

Guerrilla warfare must remain a viable combat tactic.

Nozh's blog lays out the basics of speed, the way things were, and the way things will be.