I could be wrong, but I think that one of the main benefits a brand could get from hosting a Mastodon instance is having your brand name tied to accounts all over the place. I notice this in the context of Vivaldi and the upcoming Mozilla servers.
The domain would work as a subtle, muted ad. The more users you can host, the more users you can acquire, and thus your brand permeates the Fediverse. More and more people will see @users@yourbrand.social.
The instance itself could also advertise the brand back to the users of the instance. Certain spaces on the web app can be changed to display the name of the company or service instead of the Mastodon logo. Vivaldi.social seems to do this already. I can imagine Mozilla could take it a step further not only with their logo but also with unique themeing, and thus differentiate their landing page from other servers.
Caption: Screenshot of Vivaldi.social local timeline with Vivaldi Social logo in the top right corner.
My question is, how valuable will that constant repetition be even if Mastodon becomes big time competitive?