The summary is pretty good, but the actual article is available and isn't much longer: http://www.archaeology.org/0905/etc/insider.html

I understand if someone makes a fake de-novo, and passes it off as antique - that can really mess up knowledge of the past.

But what is the difference between a replica of an item made today, and an item made in the past, if both are made by exactly the same methods?

They are identical - both were made by humans, both are made of the same thing, and by the same method, just one had some time go by. Why does that matter?

Long-term, the entire antiquities trade as based on "authenticity" is doomed anyhow. It's all just atoms, and manufacturing will eventually defeat any useful detection method.

'Course, "long term" is still like 50 years away. But I would definitely suggest strongly against investing in antiquities if you're looking to invest on that timescale. This is merely the leading edge of what will become a pervasive problem, and devaluation will probably be ongoing even in the short/medium term. The same 3D printers that sometimes show up on HN will be getting sent to scam artists with motivation to cheat. Only the very high end of the market, populated by people who care enough to take increasingly paranoid security precautions, are going to have anything that holds anything like "value".

(Obviously, I'm speculating.)

No, they aren't identical because as you say "one had some time go by". Most things are used, and with use, an object is changed. Secondly, "exactly the same methods" is questionable, depending on how old an object is. You can't just make things by exactly the same methods in many cases. And finally, there are entire civilizations that have been wiped out, so even an exact replica of something created by a member of such a society could not be recreated today. Good article though.

One of them has a story, the other doesn't. People care deeply about stories.

Yes. As an interesting aside, some famous forgeries acquire their own stories.