What exactly is the advantage of deflation over inflation?
You appear to be saying that if Johnny Doe saves 200 bucks in his trailer and they increase in value over time, it somehow advantages him compared to Sir John Doe who has stashed away 20 million in the cellar of his mansion that increase in value at the same percentage every year and also owns shares in several corporations that increase in value even more. Why?

Regarding the need for legislation, how does the market account for environmental problems for example? Most peoples' economic (and other) interests are short-term and do not take into account mid-term or long-term planning. We're not too different from Dodos who like the excitement of the jump but do not take into consideration the end result of the fall. Regulation is a means to force us onto a more sustainable path.