Apparently Magic Jack has taken some steps to cease delivering service to people who access the service with clients other than bone fide Magic Jack dongles. This happened some time in the past week and has been noted in the PBX-in-a-Flash forums as well as the Unofficial Magic Jack Support Forums.
Some offer the conjecture that such treatment of customer will in some way hurt the company. I doubt that is the case. The percentage of their users using Asterisk to pass calls to them is likely extremely small. It’s also quite likely very obvious to them, both in terms of average minutes per user per month and the reported SIP client name.