Whenever g5 is played in the world, there's someone considering taking the pawn with the knight, sacrificing a piece and going for the glory. Unfortunately, the cases when these sacs are actually good amount to approximately 3\%, according to the latest estimate.
1. d2d4  1... d7d5  2. c2c4  2... e7e6  3. g1f3  3... g8f6  4. b1c3  4... c7c5  5. e2e3  5... b8c6  6. c4d5  6... e6d5  7. f1b5  7... c5d4  8. e3d4  8... f8d6  9. e1g1  9... e8g8  10. c1g5  10... c8g4 The bishops have a curious dynamic in this variation. They are moving around all the time, pinning pieces and trying to unpin others. 11. b5e2 The bishop comes back to help the f3-knight. Both players show good knowledge of the latest developments in this fashionable line. 11... g4e6 The bishops keep moving. This one comes back to secure the d5-pawn. 11...Re8 is the most popular move. 12. f1e1  12... h7h6  13. g5h4  13... a8c8  14. a2a3 It's not very clear what this move accomplishes. 14... f8e8 A new move. 15. e2b5 It's not so easy for White to make a useful move. 15... a7a6 Asking the bishop to take a decision. Considering that White's capture on c6 is unpleasant, maybe playing 15...g5 first was more accurate. 16. b5a4 [%c_effect a4;square;a4;type;Inaccuracy;persistent;true] Who says A, must say B. If the bishop goes to b5, it must be ready to capture the knight. 16... b7b5  17. a4c2  17... g7g5 The bishops keep moving, for lack of a better option.