I can understand when an 1800 might bamboozle a 1500 rated player with a dubious/confusing sacrifice, but to see it in the Russian Super Final is another thing altogether. But to be fair to Kramnik he was never more than 2 pawns down (according to Fruit), so the Craig Skehan rule applies. For those not familiar with this rule (more of a guideline really), it is 'Being a rook down is not a reason to resign, as your opponent may blunder it back'. In the case of the following game, although Shomoev may have held an advantage, the nature of the position was that one mistake would be fatal, as it turned out to be.
(** Apologies for missing the 0-0 bug that sometimes catches me out when showing replayable games **)