"If I submit 10 ideas, where are the 100 new ideas going to come from?" Same place as the first 10, from other people's ideas. If you're an idea generating machine the DB will eventually run out of ideas to give you.

"Why would someone swap one good idea for ten bad idea?" This is answered in the FAQ. You get 4 from the top rated ones. Chances are if you haven't worked on your idea by now, you probably won't do it at all. Share your idea and you might get one or more that you will work on. Even if you don't get an idea you think it's "good" you might get inspiration from them or put a twist on these.

"What do you plan to do with "all" the ideas?" Same as everyone else who submits an idea: get inspiration.

"Would you post answer to your own questions for your own site?" I don't understand the purpose of your question.