Karl, as Mark just posted, the Hobie class rules allow Category C advertising.

As for the host of other questions by Mary and others, there are clear definitions in the rules and ISAF regs on what constitutes advertising, and what constitutes being a "Pro."

As for an OA deciding to limit advertising that is otherwise allowed per the rules of a class, that would need to be in the NOR, and you should expect that it "could" impact the turnout at your event (people aren't likely to start peeling stickers just to attend your event).

In general, this is one of those politics and religion issues, I think. There's no way everyone is ever going to get on the same side of the fence.

Since there is a variety of options available, the best course may be to decide what matters to you, and find the class and type of event that suits your preference rather than trying to change the events and classes to suit your preference.

Mike