Note that most of these solutions come from the interwebs, social networks, etc. And it isn't so much anti-sql as it is anti-relational database (sql != rdb).
The basic premise is that we need different solutions that: can scale very high for very narrowly scoped reads & writes, don't need to perform ranged queries / reporting /etc, and don't need ACID compliance. And that may be the case. Sites like slashdot, facebook, reddit, digg, etc don't need the data quality that ebay needs.
On the other hand, ebay achieves scalability AND data quality with relational databases. And when I've worked with architectures that scale massively and avoid the relational trap for better solutions - they inevitably later regret the lack of data quality and complete inability to actually get trends and analysis of their data. It *always* goes like this:
Me: So, is this thing (msg type, etc) increasing?
Developer: No idea.
Me: Ok, so lets find out.
Me: I don't know - typical approach - lets query the database.
Developer: It'll take four+ hours to write & test that query and then days to run. And when it's done we might find that we wrote the query wrong.
Developer: We had to do it this way, you can't report on 10TB databases anyhow
Me: What?!? Are you on crack? there are dozens of *100TB* relational databases out there that people are reporting on
Developer: well, we probably don't need to know what that trend is anyhow
Me: I'm outta here