Where do you draw the line between riding your own "event" on what are after all public roads and freeloading? On the Ball Buster 200 last year I got talking to a rider I know a bit and it turned out he hadn't officially entered. The event sells out very early (places open 1st Jan, sold out already, event is 7th April this year) and he hadn't secure a place. I'm not sure what he did at controls but here's the first thing: on this event, the controls are run by local charities. All the money raised by selling food goes to them. There's also a charity box (for a nominated national charity) at the start/arrivee. And I've never known them run out of food, despite being a perennial tail ender. And the second thing: this particular rider is not a big audaxer but is heavily involved in the local cycling community/scene/economy, working in a local cycling charity and used to be on the editorial team of Boneshaker magazine before that closed. I don't think his presence in any detracted from the event and probably raised a few more quid for the various charities.
He's probably not the typical "riding with my mate" non-entrant, who might simply be skimping on a few quid entry fee, and clearly it's different where there are organiser-provided facilities, as on PBP.