What's the verdict with Qa5 in the Accelerated Dragon? After

[FEN ""]
1.e4 c5 2.Nf3 g6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Bg7 6.Be3 Nf6 7.Bc4 Qa5


Does White have to castle here? If so, what is wrong with 8...Qb4?
In master level games (2400+ for both) 8. 0-0 is the only move. 

White scores rather too well (34% wins) after 0-0, with black having 15% wins.

Including lower rated players white scores 38% wins vs 28% wins for black after 8.0-0. Thus this is very playable at lower levels.

Now about 8. ... Qb4 it appears dubious at higher levels but worth the shot in a regular game.

The sole high level game Solak (2566) vs. Djukic (2402) Serbian Ch 2007 proceeded as follows:

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[White "Solak, Dragan"]
[Black "Djukic, Zeljko"]
[Date "2007.08.29"]   
[WhiteElo "2566"]
[BlackElo "2402"]

1. e4 c5 2. Nc3 g6 3. Nf3 Bg7 4. d4 cxd4 5. Nxd4 Nc6 6. Be3 Nf6 7. Bc4 Qa5 8.  O-O Qb4 9. Qe2 Ng4 10. Nd5 Qd6 11. Qxg4 Bxd4 12. Bxd4 Nxd4 13. Rad1 Qc5 14. e5  Ne6 15. b4 Qc6 16. Bb3 h5 17. Qh4 g5 18. Qe4 a5 19. a3 axb4 20. axb4 b5? 21.  Nf6!+ exf6 22. Bd5  1-0 


and white converted his exchange, overall very uncomfortable game for black even without blunder.

Also 9. Bb3 seems good for white too as 9. ... Nxe4 appears bad:

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[White "Hofmann, Brigitte"]
[Black "Kratochvilova, Magdalena"] 
[Date "1973.06.??"]

1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 g6 5. Nc3 Bg7 6. Be3 Nf6 7. Bc4 Qa5 8.  O-O Qb4 9. Bb3 Nxe4 10. Nxc6 dxc6 11. a3 Nxc3 12. Qf3! Ne2+ 13. Kh1! Qh4 14.  Qxf7+ Kd8 15. Qxg7 Bh3 16. Qxh8+ Kc7 17. Qe5+ 1-0


Similar play proceeds after 10. .... bxc6

So if 9. .... Nxe4 is not playable then 8. ... Qb4 is questionable