It seemed strange - you can eat walnuts on Passover but not peanuts. Huh? My coworker sent me this explanation:
Peanuts are not nuts - they're legumes. Just like peas and beans. Walnuts and pecans and filberts and pistachios and macadamias and almonds are all tree nuts so are considered OK even if you can make flour (of sorts) from them.
Rabbis have told me before that its unwise to try and determine "the mind of God." Fair enough. But I think we can reasonably assume that these laws were put into effect to prevent us from eating certain things. 3,000 years ago, we didn't have the ability to properly store and label things, so we decided to be safe and not eat nut flour because they resembled other kinds of flour. Today, we no longer confuse one type of flour for another - the FDA, weak as it is, wouldn't allow it. And yes, it would be strange to suddenly be able to eat new foods on Passover, and create new traditional recipes, but so what? After a generation it would be forgotten, and people would still be keeping the laws of Passover but with a little more variety.