I have known for some time that the practice of "slamming" was not exclusive to the domain name industry. In my business we are well acquainted with outfits like
Domain Registry of Canada and others. There are other related "business models" in the online space: trademark monitoring "services" that look like they come from an official source, nebulous business "directories" you're supposed to "renew your listing" in. These often look like invoices, run several hundred dollars and probably bank on the fact that a certain number of accounts payable departments will just treat them as such and remit payment on them.
We almost got stung in an offline counterpart to the domain slam: A company calling themselves
Ontario Energy Savings came to our door and nearly slammed us over to their company for a 5-year contract on gas.