The whole @gmail.com thing also opens up potential regulatory issues depending on the details of the business.

It’s a bar.

I’m probably missing some big detail, but I don’t get why he has his current setup to begin with.

The post makes it sound like he has a bunch of automation he likely wrote himself on incoming mail, but he wants Google to do some messy parts (spam filtering, archiving, providing a nice client). Google has no reason to want to continue doing that for him and the handful of other people doing something similar.