There is a difference between cross breeding and developing hybrids and going in and manually changing DNA at a molecular level or inserting dna that is not part of the species. I'm okay with the first (although I think we have bred all the flavor out of most of our food in search for prefect look, long life, and transportability) but I think we open ourselves up for problems when we start introducing foreign DNA into plants and animals or turning on and off different markers.