In a G+ post from Ingress, it was announced today that a new medal event is starting this weekend. On July 13th at 12:01 AM GMT and ending on July 22nd at 11:59 PM GMT, Every UNIQUE portal that you neutralize will count towards this new medal. The Cassandra Neutralizer Medal has 3 tiers. Bronze with 100 neutralizations, Silver with 300 neutralizations and Gold with 1000 neutralizations. To help you keep count, there will be a new stat added to the scanner so you can see how you are doing.
It will take roughly 100 unique portals neutralized a day to get gold, so stock up on those supplies! We would also advise against creating backpack accounts to deploy on portals for you. As this is not only cheating, it would also be very easy to spot and fall under win trading as well.
Uniques only mean, unique during this timeframe: