Reporting the content since site is down:

Tl;dr: researcher is browsing source code of a research paper's web page and finds a strange link (but same domain). She clicks and is informed that her IP is banned for automated spidering.

Apparently, this research site is meant to be open-access...

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Pandora is a researcher (won’t say where, won’t say when). I don’t know her field – she may be a scientist or a librarian. She has been scanning the spreadsheet of the Open Access publications paid for by Wellcome Trust. It’s got 2200 papers that Wellcome has paid 3 million GBP for. For the sole reason to make them available to everyone in the world.
She found a paper in the journal Biochemistry (that’s an American Chemical Society publication) and looked at http://pubs.acs.org/doi/abs/10.1021/bi300674e . She got that OK – looked to see if they could get the PDF - http://pubs.acs.org/doi/pdf/10.1021/bi300674e - yes that worked OK.

What else can we download? After all this is Open Access, isn’t it? And Wellcome have paid 666 GBP for this “hybrid” version (i.e. they get subscription income as well. So we aren’t going to break any laws…

The text contains various other links and our researcher follows some of them. Remember she’s a scientist and scientists are curious. It’s their job. She finds:
<span id="hide"><a href="/doi/pdf/10.1046/9999-9999.99999">
<!-- Spider trap link --></a></span>
Since it's a bioscience paper she assumes it's about spiders and how to trap them.

She clicks it. Pandora opens the box...
Wham!

The whole university got cut off immediately from the whole of ACS publications. "Thank you", ACS

The ACS is stopping people spidering their site. EVEN FOR OPEN ACCESS. It wasn't a biological spider.
It was a web trap based on the assumption that readers are, in some way, basically evil..
Now I have seen this message before. About 7 years ago one of my graduate students
was browsing 20 publications from ACS to create a vocabulary.
Suddenly we were cut off with this awful message. Dead. The whole of Cambridge University. I felt really awful.

I had committed a crime.
And we hadn't done anything wrong. Nor has my correspondent.
If you create Open Access publications you expect - even hope - that people will dig into them.
So, ACS, remove your spider traps. We really are in Orwellian territory where the
point of Publishers is to stop people reading science.

I think we are close to the tipping point where publishers have no
value except to their shareholders and a sick, broken, vision of what academia is about.

UPDATE:
See comment from Ross Mounce:
The society (closed access) journal ‘Copeia’ also has these spider trap links in it’s HTML, e.g. on this contents page:http://www.asihcopeiaonline.org/toc/cope/2013/4

you can find

<span id="hide"><a href="/doi/pdf/10.1046/9999-9999.99999">
<!-- Spider trap link --></a></span>

I may have accidentally cut-off access for all at the Natural History Museum, London
once when I innocently tried this link, out of curiosity.
Why do publishers ‘booby-trap’ their websites? Don’t they know us researchers are an
inquisitive bunch? I’d be very interested to read a PDF that has a 9999-9999.9999
DOI string if only to see what it contained – they can’t rationally justify
cutting-off access to everyone, just because ONE person clicked an interesting link?
PMR: Note - it's the SAME link as the ACS uses. So I surmise that both society's outsource their web pages to some third-party
hackshop. Maybe 10.1046 is a universal anti-publisher.

PMR: It's incredibly irresponsible to leave spider traps in HTML. It's a human reaction to explore.