The world would be way more dangerous, and it would be quite the thing with pokemon rights...(hey, why build giant eletricity generators when you can just take some pikachus and make then run?)
I think i remember one manga having ratata as a problem, same as the other toxic-pokemon-thingy(forgot the name :) ).
And bestiality would be way more common with some pokemons resembling humans so much.
(how to resize images? ._.) inside spoilers it's normal... ok