I must say a big "THIS" to what Mike's posted. The decision to race / not race falls upon the PRO and their experience and common sense. That's why the best PROs are racers. They have the judgement to know when enough is enough.
Chase boats: The HCA Championship Event Manual (orginally authored by PU, revised by me last spring) does not require a specific number of mark / safety boats, but recommends a minimum ratio of 1 mark boat to every 10 boats racing. We've been fortunate enough to be able to meet that standard on most major events. Of course if the conditions are mild, then these boats sit around. I can tell you for a fact that when the thunderstorms came through on the H-20 NAs in South Dakota last year, 5 mark boats weren't enough for the 35 boats we had racing. Things can go to hell very quickly and the PRO has to anticipate it.
Re: Waivers: I said it before - a waiver is just a speed bump on the way to court. The presence of one will not keep you from being sued. Jack - US Sailing forbids the types of waivers you posted. Rule 82 (a US Sailing prescription) does not allow Hold Harmless or Indemnification agreements as a condition of entry.