The same question is inevitably raised any time that TOR hardware hits the market, “Why buy something when you can get the same thing for free?”
You do not need specialized hardware to run TOR, you only need to configure your browser – in fact, these days you can download a browser that is preconfigured to run TOR. Why bother? I can think of a couple of reasons. A while back we did an article on Onion Pi, a DIY TOR gateway which uses a Raspberry Pi backbone – and which I inadvertently forgot to publish). The article lays out a number of reasons for having dedicated TOR gateway – these reasons are just as valid for the Safeplug, so there is no reason to repeat them all here. To summarize: you are more likely to know when your connection is anonymized and you are more likely to use TOR when you have a dedicated connection. Onion Pi was a great project and is still a worthwhile build, but at $95 it costs almost twice as much as the $50 Safeplug.
It sounds almost too good to be true. PogoPlug has built some amazing personal cloud devices and I have no doubt that Safeplug will continue in that tradition – but they have thrown a serious curveball with the activation requirement. Why build a piece of anonymization hardware that you need to register? To be fair, the activation procedure is in place for most of their other hardware, and I am sure that it is simply in place to better facilitate the web-based management of the device, but if you are seriously worried about your information security then that has to be a pretty big red flag. Activation is likely the price that must be paid for ease of use, but in these paranoid times I cannot help but wish that PogoPlug offered a user-configurable option without the activation requirement.