If there are money prizes, it means that someone is throwing money at the sport, and probably not just to make the winners happy. Chances are the same spender will be throwing money at advertising and media coverage to get his goals realized. With that would come more money for race organizers (and therefor for the organizing clubs). So in the end, if money prizes mean more visibility for our sport, it should be a good thing (assuming visibility equals vitality, and assuming we all care about vitality of the sport).
But the day money prizes will be so significant that people will derive real income from them, that day is far away. It should be a "nice bonus, extra drink money" but bigger money prizes may trigger all sorts of negative side effects that I would gladly pass on.