Sorry, but the global write lock has been public knowledge since the very early days. Mongo's done nothing to hide that. Also (i worked for 10gen at the time) the "marketing department" that you refer to, was a single person organizing events to give developers what they wanted: knowledge and a community around mongodb.
I think it's really less that 10gen itself was trying to mislead people, and more that the community itself was building up a strange mythos with little relation to reality. This, unfortunately, tends to happen rather often (node.js is magic! Java is really slow! etc.)
That's what made me drop research into NoSQL a couple of years ago- the overly optimistic and magical thinking seemed to be really pervasive. I don't want to get burned from joining in a group delusion. (I'm not trying to say that's what's going on specifically in Mongo or anything else, just acknowledging that the mythos phenomenon mentioned above can repel me.) Since you've coined the term, are there any NoSQL projects you've seen that don't suffer from the mythos issue?
It varies, a fair bit. MongoDB is perhaps the worst, possibly because it's easy to get up and running with, and behaves a little magically (you don't need to know how it works to use it, or at least so you might think initially). It also has a company pushing it, of course.
I'd say that this is less of a problem for the Dynamo paper databases (Riak, Voldemort, Cassandra), because really to use them at all you have to have some idea of what's going on.
I'm a bit biased here, though, while I've found Voldemort, Redis and Cassandra useful and can see Riak and a couple of others being useful, I could never really figure out a good reason that anyone would use MongoDB besides naiveté. That said, I've never really tried, as I don't have a problem that fits it (part of my issue is that I don't know what a problem that fits it would look like).
Judging from the fact that this same behavior does _not_ occur on the apple.com site, which is running the same exact promo of the iPad mini, my guess is that this is something new and not the existing behavior.