The problem with the Frihost concept is that it encourages a large amount of random posts in order to gain points.
I think it would be a good idea to give people extra points for each reply a topic recieves. This way, people would be encouraged to come up with good, high-quality topics in order to garner a large number of replys. This way, we could keep the quality of Frihost high.
I'm not sure exactly how the Frihost cash mod is made but I can only assume that to change it would be very labour intensive.
I also find that the actual theory isn't all that good. If you look in general chat a lot of the spam toics of which is your favourite etc are very popular. This is because people can get points in those topics easily. Another example is where people simply arent interested. For example if I started a big discussion on creating cookies in PHP only those that knew php I would assume would join in and then only those that could be bothered etc.
Basicly although a nice idea, I personally just cant see it working.
I don't think that would help. Some topics get HEAPS of replies, without any real discusion (eg. what's your favourite game.)
I actually think this would generate more topics that dont really need to be here, people making a new topic in hopes of it generating lots of replies, thus there would be more of a reward for making new topics than replying to already made topics.