Not necessarily. There could be many reasons. Carnival has 22 ships so more ships to ask questions about. Could also be people that travel on more upscale cruises tend to use travel agents more. Therefore; they don't have as many questions because their travel agent takes care of them. There could be many reasons for more post.
tim c, your observation probably tells us which cruise line is the most popular; but lines like Crystal, Seabourn, Regent-7 Seas and Silversea are generally considered the best, and you don't see many postings for them here :-)
People flock to Carnival because they spend so much money on advertising, have very economical fares, have more ships, and are typically the most recognizable line. It in no way implies that they are the "best". They rank average in most categories except overall value. Carrying 35,000 passengers at any given time will result in many posts (negative and positive). Believe me... if HAL had 22 ships, you would see thousands of HAL posts. More ships=more posts. It's a direct proportion.