Blacks gives a pawn for very good piece attack in kingside with his strong bishop pair, queen and centered knight, and white hasn't developed a single queenside piece , but moved rook 3 times in the opening. so white will indeed avoid it by playing h3 or a4. I play h3 to transpose it to closed Ruy Lopez.

to get initiative!

why black sacrifices the pawn?

This is great for black if you play aggresively. You sac a pawn for the initiative and a dangerous attack. If someone plays the move order 7...O-O-O rather than 8. c3 play 8.a4 or prepare to ride the storm 

more or less balanced...but white is up on initiative...control of the centre is crucial for white..black though has chances of getting even..

Here a vote game with it:

http://www.chess.com/votechess/game.html?id=7757

It was a game, where our light- coloured bishop in combination with queen and rook dominated the game! (comments can you find in archive)

It`s a very good weapon for black!

Statistically black does quite well here.  An aggressive player can easily get compensation for the pawn.

"black is losing i think".. lol

Black is losing I think

Sharp Opening!