In Austria, the problem with cell-phone voters is the following:
When signing a cell-phone contract, you are asked if your name and phone number can be automatically added to the phone books.
Many (young) people are not allowing this.
Therefore, we have an ever increasing segment that's cell only and not in a phone book.
These people basically do not exist for pollsters, because they cannot contact them.
Don't many US pollsters actually dial random numbers within the area code in question? That would eliminate the phone book problem, because it doesn't matter if you're listed or not.