If you had asked me before round 7 what players were having a really outstanding tournament, I would have given you four names: Magnus Carlsen, who has been playing like the world champion he is; Hou Yifan, about whom I would only change the pronoun; Shakhriyar Mamedyarov, who has been successfully leading the first place team; and Rustam Kasimdzhanov, who has defeated Arkadij Naiditsch, Vassily Ivanchuk and Vladimir Kramnik. All four players lost today, in most cases pretty badly.
Carlsen had White against Naiditsch, and when he won a pawn one would have expected everything to be smooth sailing. As it turned out, it was - for Naiditsch. The German grandmaster completely outplayed the world's #1, and in the process his team was victorious as well.
Hou Yifan at least had the black pieces in her game, and she picked the worst possible time to come a-cropper. Her Chinese team really had just one rival in the tournament, the Russians (and vice-versa, with all due respect to the Georgian women), and this was the day when they met. Unfortunately for Hou, she was already lost after 12 moves (thanks to her 11th and 12th moves), and while Kateryna Lagno (aka the face that almost stopped the launch of a thousand ships*) may not have played perfectly, she played well enough to reel in the full point. The other Chinese women were unable to make up for their leader's failure, and Russia's 3-1 victory has them in great shape for tournament victory.
On to Mamedyarov. He was butchered by Leinier Dominguez, who won a great game, but - unlike Carlsen and Hou Yifan - Mamedyarov was bailed out by his teammates. Teimour Radjabov won on board two and Gadir Guseinov won on board 4, and so the Azeris beat the Cubans to take sole possession of first place.
Finally, Kasimdzhanov received his come-uppance from Hikaru Nakamura, but this was more due to Nakamura's playing extremely well than to Kasimdzhanov being in bad form. In fact, his preparation was excellent and he enjoyed a big lead on the clock, but Nakamura worked everything out, winning some material and converting his advantage. In fact, it was an excellent day for the USA, which won 3.5-.5.
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* This is not meant as a disparaging remark about her appearance, but refers to the controversy generated by her switch from the Ukranian to the Russian chess federation and the kerfuffle it raised between FIDE and the Norwegian organizers. At one point there was even talk of cancelling the Olympics, which would have metaphorically entailed scrubbing the launch of the "thousand" "ships" bringing the players to Tromso.