Blackjack hole-carding, however, is in a much grayer area. There is no doubt that those blackjack players seeking to gain an advantage over the casino by willfully peeking at dealers' hole-cards are attempting to cheat by definition, but the actual carrying-out of the process leaves things much less clear. The obvious argument against hole-carding being cheating is that the blackjack hole-carding player is simply taking advantage of the dealers who expose their hole-cards due to sloppiness and lack of following proper dealing procedure. They don't do anything to cause the dealer to expose their hole-card, even if their intent was to find a dealer that indeed does so.
This argument does hold water.
There have been some arrests of blackjack players for hole-carding, mostly in Nevada, but I am not aware of any convictions or plea-bargains by those guilty of doing so. So in summation, I guess you are pretty safe when hole-carding at blackjack, even though it is getting harder and harder to find good opportunities to do so in light of the dwindling availability of hand-held blackjack games across the casino world.