I favor open borders all over the world. This means removing almost all immigration restrictions that we have right now.
The blog openborders.info has many arguments in favor of open borders and extensively debunks the arguments against, including all that have appeared in this thread. I invite you to visit the site and to like it on Facebook.
Anyone could have had the misfortune of being born in a developing country, an oppressive dictatorship or in a war zone. While this injustice cannot be undone, we can stop forcing innocent people to stay in the miserable places where they were born in. The fear that immigrants would spread the misery from their birth countries is simply wrong.
* The evidence points to the contrary, namely that both immigrants and natives would benefit greatly from open borders.
* For each specific social problem there are many alternatives to banning people from the country for life that we already apply to natives, because they are far better.
* Even if we benefited from immigration restrictions, banning billions to slightly improve the lives of few millions is evil.