I think this is an excellent use of the G+ technology stack.
For certain dishes or chefs, I easily see foodies and aspirational gourmands paying the price of admission.
The viability of ventures like this are very dependent on the underlying technology, but more importantly they are subject to the legal attitude of the host company - I was about to say that I would be nervous trusting my product to such a high level of vendor lock-in, but I use PaaS products as often as possible (speed kills)...
I'm no design expert, but I find this extremely appealing. I would not mind sitting and browsing through all the different projects (which is hopefully the goal of the design). My emotional reaction to the site is very different than most Github pages, which have a reaction (possibly Pavlovian) that goes "Get back to work!"
Interesting story; definitely differs from the conventional wisdom regarding building it yourself. Reuse of a previously built codebase is something I can approve of... especially if your competitors are constantly reinventing the wheel.
Google has excellent tools for taking your data elsewhere; services like the Data Liberation Front (http://www.dataliberation.org/) are pretty progressive.
That said, hosting your own email is what someone like RMS would recommend as it gives you, by far, the most control and privacy. All major webmail providers are not going to provide the stability you are looking for, especially if you are bothered by the current trend towards integration.
If these are people you genuinely care about, it is worth the time investment to educate them why the idea isn't practical or useful. Keep in mind that they often do not have nearly the same insight into what it takes to really build a product or a business.
For a lot of other people (where you dont want to invest the time debating/educating them), you can offer to let them retain equity and work on it at contract rates. If you have the spare time and use for the cash, you can give them a slight discount (vs. market) and everyone wins.