Is this knight sacrifice a good idea? I often play the following variation with black when I play blitz. Somehow it refuses the known lines of the Spanish.
It looks like that black is going to be destroyed but almost always I win when I play this opening.  

[FEN ""]



1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 6.Bb3 Be7 7.Re1 O-O 8.c3 Nxe4!?   


The main idea is that IF white accepts the sacrifice, he/she is going to suffer a pawn storm who will paralyze the queen side.
Almost always (I mean over 95% of the times) the game continuous like this:   

  [FEN ""]



1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 6.Bb3 Be7 7.Re1 O-O 8.c3 Nxe4!? 9.Rxe4 d5 10.Re1 e4 11.Nd4 Ne5   


And after this continuation, black has strong attack.
I really liked the idea that I found something different to play when I am facing the Spanish (By the way, is 8... Nxe4 a "new" idea?), but I think it is possible to get crushed in a game which is not blitz.
So my question is:  


  Is 8...Nxe4 a move which gives black something good in general?
The sacrifice is quite dubious.  Besides the answers with 10.Nxe5, 10. Rxe5 is simply two knights for a rook and there is no attack for Black.