can someone explain why this opening is so lowly regarded?
I'm not an expert by any means but I'll give it a shot. The fact that it's "ok" isn't good enough. Black's first priority is to equalize. White starts off ahead by a tempo, so by default he's ahead in development. Black needs to catch up in a hurry (for mere mortals like you and me, lagging in development or wasting several tempi might not matter - your opponent won't be good enough to punish your mistakes; against a master, lag in development and waste a couple tempi - and you're sure to get mated in under 20 moves!) After 10 moves, you say Black does have a share of the center and is not far behind in development. Ok, fine - but there are other openings where black has reached equality after 10 moves!
Specifically regarding 1...a6, the rook pawns (generally) shouldn't be moved in the opening unless there's a good reason to do so: http://www.chesscafe.com/text/heisman48.pdf
Can you explain to me: what does 1...a6 accomplish? Does it counter one of white's threats? Does it bring black closer to equality? If black wants to play a6 at some point, why shouldn't he do something more constructive with his first move, and play a6 later - for example, to chase away a white piece from b5?
The reason it is not highly regarded (and this is probably true of 99% of uncommon openings) isn't that a refutation exists (as far as I know), or that black will "definitely lose" if he plays this opening; rather, it's that black has several options which are better. 1...c5, e5, e6, c6 (for example - not that this list is exclusive) all accomplish something positive and constructive for black. Meanwhile, 1...a6 does nothing to solve black's immediate problems (namely, that he is behind a tempo and white has already occupied the center).
The St. George's defense starts out with 1.e4 a6!? Most people think it's a horrible move. In fact, on Chessmaster's Opening book, this is the comment on 1...a6.
"A move with little to recommend it. It fails to stake a claim in the center or begin development."
I disagree! Let's look at the main line. Black does have a share of the center and is not far behind in development.
Does anyone know any refutations to this opening (1.e4 a6 2.c4 is a good try) or can someone explain why this opening is so lowly regarded?