In fairness, there's a cover article on this subject in the current
National Geographic and it's quite clear bringing back a particular
person isn't in the cards but bringing back a particular species may
well be.
For instance in the typical avian egg, the DNA isn't really in the
shell or yolk so if a living creature is grown in another species'
shell but is identical to a passenger pigeon is it a passenger pigeon?
Obviously with any such project you have to re-create enough of a
species to get it to reproduce - after all if you create one extinct
bird with a lifespan of 10 years - after 11 years you get extinction
again.
Similarly if the cost of producing mating habitat for an endangered
species is 1/4 million $ and there are multiple endangered species, is
it even ethical to clone a passenger pigeon from existing DNA even if
technically possible? (I'm not sure how long DNA in a feather is
viable but if it's 500+ years the dodo and passenger pigeons are two
species where a recreation is possible - but is it ethical if spending
the money on these prevents habitat restoration of 6 other species who
fail to survive?