Why? Because they are selling it without mentioning why they won't fail where every other attempt has. There are huge difficulties in this. Have they turned a corner on the research that changes something? I don't see it in what they've so hinted at so far.
First, they are Google, and therefore possess huge quantities of data and the ability, courtesy of their uber map reduce prowess and ultra-fast custom hardware, to make sense of it.
Second, they bought Metaweb (makers of Freebase) and with it some of the best semantic expertise out there. Toby Segaran is a brilliant dude. His O'Reilly book "Programming the Semantic Web" explains in 20 pages what most books take 150 pages to do: the concept of a URI based graph database and how it enables data to be merged from multiple sources and reasoned over with applications.
I only hope Google open-sources some of their research here for the rest of us.
But also, have you read any of the papers involved? Datalog is pretty simple. It's a restricted, forward chaining prolog. Once you know that, you can recreate most of it from that description alone.
http://bergie.iki.fi/blog/google-s_rich_snippets_will_lead_u...
I thought that while flawed cpedia (from one of the cuil founders) was a much more interesting push on this idea then Googles one currently is.