All people who fulfills the official criterias can be nominators. This is not controlled by the Nobel Institute, and a nomination means nothing before they are selected as candidates on the short-list by the Nobel Comittee.

Hitler was suggested as a joke by a Swede and withdrawn shortly after, and Stalin got a nomination for "his efforts to end World War II".

Again, nominations are not created by the Nobel Institute. I do agree that awarding Obama the prize was a stupid choice.