I haven't thought about this one particular provision of the law with respect to the 4th Amendment b/c I don't care to delve into detailed arguments of law - I prefer leaving that to the lawyers and Constitutional scholars to endlessly debate.
I prefer to simply look at things from a practical impact standpoint. How it effects me or others. First, it is another heavy chain around the neck of the small business owner, many of whom are put out of business by overburdensome government regulations already. This law requres the business owner, once again, to work on behalf of the government without compensation.
Second, I am not overly familiar with this provision. Would it require someone making ten $1000 purchases with cash to now have to leave a name and address with the business? What about someone making 20 $500 purchases? Will we be free to use cash at all anymore, or is the anonymity of cash too inconvenient for the government to keep tabs on all of us? Maybe we should make it easier and just requre everybody to use government issue credit cards only. After all, if we are doing nothing illegal, we have nothing to fear, right?
This provision notwithstanding, it is the cumulative effect of the entire act that bothers me. More and bigger government. More and bigger regulations. Less and less freedom. These tools will not be limited to stopping terrorists. They are simply more devices by which the government will herd the flock.