1. probably it would be costly
2. a single mistake has devastating repercussions
3. it borders on the issue of ethics and morality
4. an increasing demand for genetic modification which effetively increases discontentment for the self or for the original genetic configuration of an organism
5. prospect of creating new species might create natural imbalances especially on the habitats and feeding habits of other animals (by creating a new species, competition might arise, or it might be a predator to a prey who are already endangered, or for its own survival, it might need to destroy the habitats of others)
6. unexpected but undetected mutations can generally alter the future in unpleasant ways.