So I look at this argument going on about "Home Sharpeners" vs. retailers in a different light. I also play/coach high school tennis and have been stringing racquets for years. I started just like many stringers, getting my own and learning the craft. There are many types of machines out there, some of which make it easier for stringers to do their job (i.e. electronic stringers). Just because they're easier to use, doesn't mean you can be bad at the craft and not pay attention to what you're doing. You still need to make sure the strings aren't slipping in the clamps, the weave is correct, you've started in the correct spots and your tensions are accurate. The same goes with this machine.
As for the "home sharpener" taking business... that's called capitalism, folks. If you don't provide a good sharpening all the time or people don't live in an area that has a lot of stores with good sharpeners around, those people are going to seek out better options. I don't have a Sparx, but I'm heavily considering one if my youngest decides to start playing. If people start asking me to do it for them, I'll give them the same speech I give to the people I string for. I'm not trying to take business away from the local shop, but if you feel this is a better experience for you, I'll gladly do it.
Are there people who will try to take advantage of this? Yes, there always are. However, most people are doing it to provide a better service or convenience to people they already know. If they're not doing a good job with it or it's not what they're looking for, they aren't going to continue to come back.
Lastly, remember how many of you sharpeners started doing this as a hobby or interest and then turned it into a career. There are plenty of people who are fortunate enough to have a shop and do this for a living, but many people like to learn a craft and will provide their services to a small subsection of the population for a nominal fee because they enjoy it, not because they're making $5 a sharpening.