Not only that, but clearly the service is aimed at making harrassing calls. Making such calls is illegal, is it not? So here we have a business who's only line of service is set up to make illegal harrassing phone calls.
I'd think they would be pretty easy to shut down under the RICO statutes. Could make a pretty good "criminal enterprise" argument. I doubt they'd be able to do much to protect anyone if their ISP access logs are all subpoenaed by some DA.
If ya DO use it, use an anonymous prepaid debit card, and only go to their server via an anonymous proxy!