I'm not a grandmaster, so my verdict has not the power of law. Yet if I look at the figures, I'm inclined to think are they insane? If I see grandmasters memorizing lines 20 moves deep or more, I get the feeling they are fooling themselves and each other. Isn't it just a matter of fashion? Let's try to use some reason.
Fischer suggested that openingstudy would kill chess in the end. In order to prevent that, and to become independant from the study of openings, he invented his shuffle-chess. Since Fischer chess has 960 different start positions, the amount of openingstheory becomes 960 x so vast. That raises the following question: can we create the same effect without altering the rules?
At every ply in the opening there are about 20 possible moves. If 5 of them are mainstream theory and 15 "unorthodox", you need only 3 plies where you make an unorthodox move. That gives you 15 x 15 x 15 = 3375 new possibilities. Are all these possibilities automatically bad since they are not part of the "theory"? That is hard to believe.
Have a look at the following table from my database with 650,000 mastergames.
It lists the moves that are played by white after 1.e4 c5 2.Nf3 d6
81.6% of the whiteplayers play 3.d4
Why on earth is that so? I have never heard a reasonable explanation why d4 should be the move. If you look at the figures, both in practice and according to Rybka 3.Bc4 should be the move. So why is everybody trading a fat centerpawn against the pathetic farmer at c5? Leaving black with a stronger center and an open line further away from the king? With a ready to exploit minority attack?
Is it just fashion? Do people fear to think for themseleves? Even masters and grandmasters? The figures suggest that even they behave like sheep.
While I got better at tactics, I felt more and more independant of the opening. Of course I don't know how that will be at grandmaster level, but I would test the hypothesis for sure if I was one of them! If it is possible to get rid of openings study by such simple means, you could use your time for different topics, more worth to study.
After 2 hours calculating and 19 ply deep Rybka comes up with 3.Nc3 as the first choice (+0.09) and 3.Bc4 as a second choice (+0.07). I suspect that it will come closer to zero if I let it run longer. To my knowledge these openings haven't even a distinctive name!
So if you know what you are doing and your opponent does not, openingstudy can give you an edge. But if you don't want to study you can force anybody in unknown territory in just a few moves. Without being worse than in the mainlines. Then you must both play chess as early as move 5.