Not only does Cruelty appear to be a real card, it appears to be a darn good one.
Zadok, I certainly see your point about the Flashback cost not being included in the reminder text. But I see no reason that WotC can't make a change like this. After all, it was once true that everything that said "Counter target spell" on it was an interrupt. (Aside: On cycling, didn't it strike you as a little strange that every single cycling cost was 2? Why not just have tha bility "Cycling" with reminder text explaining that it cost 2?) In any case, I think that repeating Flashback costs in the reminder text would be ugly and cumbersome -- I think the same thing about buyback cards -- so I'm fine with the new style of wording it.
On Threshold and Millstone:
It sounds like a good idea at first, but this has almost certainly been taken into account and tested in the "Future Future Next Tuesday League of the Future" and it's likely been found that such a strategy has certain drawbacks. I'm willing to bet that you can get cards into the graveyard just as efficiently by playing them (non-permanents, of course).
Flashback, in fact, seems like a mechanic that would have more interesting Millstone interactions. Actually, the ability seems designed to screw control decks altogether. Countered? I'll play it from the graveyard. Forced to discard it? I'll play it from the graveyard.
With two abilities like this in the set, it seems a certainty that removing cards from the graveyard will be a theme on some cards as well.
One more note, in anticipation of the argument that's dominated this subject on the MTGnews board. The Flashback wording does not remove the spell from the stack before it resolves. First, it's an ability, not an instruction. Second, it's reminder text, not rules text.