A couple of potential problems.
1) The ice has oxygen in it. If added to hot wort it might cause Hot Side Aeration. Many people believe HSA is a hoax, but I bet most of them still minimize the potential for it. I believe it is real, but takes a lot of abuse of the hot wort to get it.
2) If there is any bacteria in the ice, you are giving it a great environment to reproduce and spoil the beer. There is always bacteria in the wort; we don't sterilize anything (apart from possibly the wort itself with the long boil), we only sanitize, so everything has some bacteria on it, and there is always bacteria in the air. When we pitch yeast, we generally pitch a healthy amount, and it becomes a race between the yeast building it's colony and creating alcohol to protect the beer, and any bacteria building it's population to a level to which it can affect the taste of the beer. The bacteria grows and establishes itself quicker than the yeast, so we need to keep any bacteria to a minimum while maximizing the yeast. This is probably your biggest potential problem - you don't know the quality of the water that made the ice, so you could be adding bacteria; someday you will get a bad bag of ice, or the yeast you pitch will have a problem leaving more time for any bacteria to multiply.