I concur.
Facebook has nearly pulled off what AOL did when the WWW was young, allowing many users to believe it was the entirety of the Internet, and not just a BBS community and Internet gateway provider, which is all AOL was. Facebook is a website, so maybe this accomplishment is even more impressive. As with AOL, the sheer volume of Facebook membership means it should not be ignored for marketing and sales. But so many FB members with commercial interests exclude the rest of the Internet by embracing only Facebook, and I, for one, will never join Facebook.
At least McGizmo has a website of his own and an active membership at CPF. Facebook and CPF probably offer convenience and comprehendability for McGizmo, who is just one man. But other than the understandable resistance to having to administrate a more complicated site, growing too quickly may be another reason he might not want to set up commercial sales and marketing under his own domain (by hiring a competant pro web developer, and coughing up the $50 it may cost to automate "buy me now!," just as it is automated at eBay, Amazon, and even far smaller vendors).
McGizmo does show some toes in the water, so to speak, maybe up to his knees, of web development on his own, so I doubt he hasn't considered this: once it gets up to your neck, if only throwing the terminal in the ocean could stop the ever growing attention it requires. The next step, of expanding his own domain, could be a real headache, even if everything goes smoothly, the possible avalanche of expected new sales, and too many customers with too many impatient demands of "where's mah flashlight!"
Facebook is more easily ignored when necessary, to maintain autonomy, and still be able to surf during business hours, than domain-specific sales and possible government agency scrutiny (from fickle customers that fire-off grievances without understanding).
I think Don's customers are opposite, and he likes it that way. You can not choose the McGizmo. The McGizmo chooses YOU!