But creating a cloned embryo requires human egg cells, and egg cells aren't cheap.

FORBES: Cloning's High Cost

Put on the ballot by a home-schooled Baptist woman, this would define a fertilised human egg as a person.

ECONOMIST: Ballot initiatives

That process requires human egg cells, which must be donated by women.

FORBES: Magazine Article

Eggan's technique, which is the subject of a paper in the current issue of Nature, creates stem cells specific to a particular disease, like cancer or diabetes, without a supply of human egg cells.

FORBES: Stem Cell Science Heats Up

But critics of human cloning and stem cell extraction methods essentially believe a human egg that begins to divide for any reason should be considered an embryo, and a potential person, that deserves protection under the law.

CNN: Democrat blocks Senate debate of cloning ban

They seem to have figured out a way to produce an unlimited supply of clones efficiently-- which means they either use a completely different method to create those clones, or they have an unlimited supply of human egg cells.

FORBES: Scientists Fret Over 'Clones'

But with human beings, egg cells must be taken from women through a difficult medical procedure.

FORBES: Scientists Fret Over 'Clones'

In order to clone a human, scientists would remove the nucleus of an egg and extract its genetic material, leaving just its shell.

CNN: Group says it will move human cloning work offshore