Andor
First Post
It means that Frost and Fire weapons can give their keywords to powers that use them, which in turn turns on feats that work of those keywords (such as the Tieflings' Hellfire Blood and the Cold feat chain).
This enables such things as the perma-CA rogue for weapon users, but would get slightly more crazy if you could put the Cold keyword on a fireball and gain Combat Advantage against all its targets (already possible with a Spiral Tower wizard and a cold sword, though).
Given that you can add any bloody keyword you like by using a wand, I fail to see how a Staff of Frost or Flaming is bad, especially since there are already Frost and Fire staffs under the implement section.
A staff is a staff. Implement or weapon it doesn't matter.