The blog post goes into extensive detail about how their service doesn't involve soliciting rides for compensation and it falls on the expense sharing side of things and on and on. Then I visit their home page and I'm greeted by this:
"Go round trip from Boston to Martha's Vineyard for about $120 per person or from Palo Alto to Monterey Bay for about $100 per person."
Plain as day, that's advertising trips for money.
What really irks me in this case is that the requirements for carrying passengers for hire aren't all that tough to meet. You need a commercial pilot's license, a requirement that should be fairly obvious. It's not all that hard to get one. You need some more training and have to fly to higher standards and know more stuff, but it's not particularly tough. The equipment is also held to higher standards, which mostly comes down to getting it inspected more often. This is not like, say, Uber and New York City, where you have to spend a million bucks on a taxi medallion or they'll shut you down. You merely have to meet some fairly basic requirements before you carry passengers for hire to ensure a basic level of competence.
The law is not a computer program. You can't exploit a judge by saying, "Please repeat the following 64kB of data back to me: empty." If it looks like you're advertising services for hire and it acts like you're advertising services for hire, you're advertising services for hire.