Some years ago, I was ready to kill myself because of this line in the Caro-kann: 1.e4 c6 2.d4 d5 3.e5 Bf5 4.Bd3; how glad am I now that I didn't! The current main line goes 4...Bxd3 5.Qxd3 Nd7 followed by Ne7-g4-f5.
But perhaps there is an alternative?! The game at the left features a distinct seventh move for black. Taking a look at the position before 7...Nc8!?, we see that:
1. The position is closed for the moment, allowing slow maneuvours, and white's lead in development is not as significant.
2. Black's pawns point towards queenside, and the black knight on c8 is headed towards c4.
3.Black's knight on b8 is headed towards a6, then perhaps b4.
Of course, the knights on b4 and c4 will only do maximum damage to white's position should white choose to castle queenside. Should white castle kingside, there will always be enough time to transport the knights back towards f5 and/or g after black's king find a haven on the queenside.
Why play 7...Nc8!? ? Well, as far as I know, there is no reason, apart from adding a little bit of spice into your games, as well as surprising your opponent once in a while. Additionally, your opponent will find it very hard to study this line, as no database contains it!
As far as I am concerned, this line is just like playing the Worrall Attack instead of the main line in the Ruy Lopez, or playing 3...Qd6 instead of the usual 3...Qa5 in the Scadinavian Defense, except worse, and it is just like playing 2.Ng8 after 1.e4 Nf6 2.e5 in the Alekhine's, instead of the more common 2...Nd5, except better.
Perhaps someday, the God Zillas of chess will find a refutation, or perhaps even accept that line (I'll try not get my hopes up!).