Nope, no coordination nor conspiracy.
I reviewed the book at my own schedule, and as far as I know O'Reilly Media planned their Cyber Monday without any connection to when this review would be posted. Slashdot didn't promise me a posting schedule anyway, although a few days ago an editor wrote to say he'd probably run it on Monday. I forwarded that fact to a couple of people at O'Reilly (see below), but that was on Thursday, which was the Thanksgiving holiday in the U.S. Suffice it to say it is highly doubtful that O'Reilly Media planned their whole Cyber Monday thing starting a mere three days before the event and over a long holiday weekend!
However, I should have added a couple of disclaimers to the review:
O'Reilly sent me the copy to review, and, more importantly, the editor on the book, Andy Oram, is also my editor. The free review copy is not really worth a disclaimer, though; I'm just trying to be thorough. First of all, the amount of time it takes to read a book and write a review far outweighs the cost of purchasing a copy, and second of all, as an O'Reilly author I'm pretty sure I could have just emailed them asking for a copy anyway, regardless of whether I were reviewing it :-). As for sharing an editor: while Andy's a friend, I know he wouldn't want me to write a review differently just because he were the editor, he knows I wouldn't do so anyway, and he knows that I know that he knows I know he wouldn't want that. (The two people at O'Reilly whom I emailed about the probable Monday posting were Andy and the person who had sent me the review copy.)
So, this was not a slashvertisement -- just a coincidence, to the best of my knowledge.