First of all, Yes that is a picture of Karen's dogs on the front page of the Iditarod home page.
Dropped dog number three is Olena. She had two strikes against her, sore shoulders and she is in heat. She was coming into heat before the race started, and it wouldn't be the first time that a dog in heat ran in Karen's Iditarod team. Sissy was bred buy Butch in the 2000 Iditarod. Karen tied Sissy to the sled so no one could get to her, but Butch manage to drag the team around while Karen wasn't paying attention. I don't know who dog number four is.
Don't worry too much about Karen's team shrinking. We train all Fall having 10 or 12 dog teams pull 600 pound four wheelers for 50 to 60 mile runs. So this should be a walk in the park. You only have to have five dogs to cross the finish line. As Karen's team gets smaller, she will get rid of the sections of gangline that are no longer required, giving her a smaller more compact team to work with. Also all the food and snacks that were sent out along the trail are sized for a 16 dog team, so now Karen has 25% more food then she needs. Less feet to take care of, less straw to haul around, less food to dish out all means more time for Karen to sleep.
Here's a tip on how to read the update sheet. You may have noticed that the column labeled "SPEED" has a musher running one sections at 4 miles an hour and others at 12 miles an hour. This is because in the longer sections the teams rest on the trail and the clock keeps running. The rest time gets figured into the speed and you don't know how fast the teams is actually moving. Okay here's the tip part. Take the teams speeds between Grayling and Anvik on the way down and between Anvik and Grayling on the way back, average them and this should give you a pretty good idea of the speed that the teams are traveling. The trip is only 18 miles both ways so no one will be stopping along the trail.
Also when you post a note on the "Root for your Musher" section on the Cabela's page, make sure that you make the title fairly obvious that it's for Karen. She not the only musher out there.