seriously, I asked ROHM (or another company, it was college days) why the 0 ohm resistor have power rating, the support person can not answer the question directly... 
@sevenstring
hmmm...mukhang para sa CS5463 yang resistor na yan...majority manganin wire gamit, although may application notes sa Maxim kung paano gamitin yung PCB trace (for a DC current sense)...hindi ko mahanap yung application note...
I know this is an old thread but i can't help but comment. You should ask yourself first if it really has zero resistance. Remember that resistance is inversely proportional to area. And if it really has a very small resistance (and im sure it is not zero), it will change when it is subjected to temperature if its area is not that big.
Search for low resistance devices. They are in milliohm or even uohm, so needless to say, there is no zero resistance as in perfect zero. And if I was the support person, there is always a power rating because of the max current rating of that device (if it exists), he was just not that informed. That max current and the minimum resistance (at ambient temp) can be used as the power rating.
