There are currently 2 posts about csgo on /r/all[1] about the Fnatic game so I will sum up what has happened.
Counter-Strike: Global Offensive is a competive first person shooter. There are 4 major tournaments each year with a prize pool of $250k each time. One of these events called Dreamhack Winter is going on right now. One of the quarterfinal matches was between a team named Fnatic, and LDLC. These teams have been recently called the best teams in the world, but Fnatic has been involved with a lot of controcersy lately. Many of their players have been called hackers, but nothing has been proven
In the game that just happened Fnatic was losing by a huge margin (3-13). The fnatic players used a "boost" to get to a portion of the map that they would not normallyy be able to go. These types of spots are normally legal, and encouraged, but this specific boost gave Fnatic a view of the entire map, and easily won them the game. Many players are calling this very scummy.
Here are some key points about the boost:
Fnatic has known about this boost for two months and didn't tell anyone.
The boost may have been an example of "pixel walking" which is is not allowed in the tournament.
Apparently the team asked a reddit user to remove a video demonstrating this spot several days ago so other teams didn't see it.
Here is a screen shot of the boost: http://i.imgur.com/AFVdPGT.jpg [2]
Please feel free to add anything and I will add it to the main post