What's wrong with 1.b4?

What are the main tactical traps in a 1.b4 opening?

The wire your opponent strung behind your chair so that when you stand up you'll fall over. 

There are several things wrong with it. 1...e5, 1...d5, 1...Nf6, 1...d6, 1...c5, 1...g6, to name a few.

1.b4 doesn't help you too much with your pieces development.So, against a good prepared player you can't surprise him with this, and he will obtain equality more easily than in d4,e4 openings, where you can get an opening advantage.

1 ... e5 is met by Bb2, as are the others, with the exception of 1... c5 which can be met by 2. bc.

A. Adorjan has once proposed the following setup:

1.b4 e5, 2.Bb2 Bxb4, 3.Bxe5 Nf6, 4.e3 d5, 5.c4 0-0, 6.Nf3 Be7! (preparing c5 which restricts the white central pawns), 7.Be2 c5, 8.0-0 Nc6, 9.Bb2 Be6, 10.cxd5 Nxd5 and Bf6.

There is no spatial superiority of white in the centre. Furthermore, in an endgame the black queenside majority could be annoying

ECO or MCO I forget which, had only two pages on this opening, but with a note that it was "better than its reputation".

ECO or MCO I forget which, had only two pages on this opening, but with a note that it was "better than its reputation".

I also like a King's Indian setup, because b4 plus Bb2 is not the best start of a White attack on the queenside. Such an attack is more dangerous with b4 and Rb1 ( and not closing  the b-file with a Bb2, the bishop is more useful on e3 or d2). 

1.b4 e5, 2.Bb2 d6, 3.c4 Nf6, 4.Nf3 g6, 5.e3 (g3 and Bg2 is of course also possible) Bg7, 5.Nc3 0-0, 6.d4 Nd7.

(The game here resembles a variant of the King's Indian Attack, but with changed colors: 1.e4 e6, 2.d3 d5, 3.Nd2 Nf6, 4.Nf3 c5, 5.g3 Nc6, 6.Bg2 Be7, 7.0-0 0-0, 8.e5 Nd7, 9.Re1 b5 etc. The ideas of that opening are useful for the Sokolski 1.b4, too. ) 

If White castles kingside, Black will push the pawn e5 to e4, and try a kingside attack  with Re8, Nf8, h5, Bf5, Nh7 etc.

If White castles queenside, then Black can react flexibly with c6, opting for an attack against the white pawn chain d4-c4-b4, as well.

As white, I would play 3. f4 rather than 3. bxe5. Just my opinion- white needs to keep the center open and at least on my level you can often win the h8 rook. 

Fischer played this opening move in a simul against Walters and won.  I would recommend though that only GM level or higher player attempt to use it in tournament conditions.  http://www.chessgames.com/perl/chessgame?gid=1255196

This B4 opening is not totally unknown.  Capablanca also used it in a simul and lost!!!!!

#sarcasm #smartalec

It really is not a bad opening if played with some general knowledge. It isnt overly theoretical, but one needs to understand the goals of the system.  this book does a good job in explaining those if anyone is interested: 

http://www.amazon.com/Play-1b4-opponents-Sokolsky-Everyman/dp/1857445600

Michael Basman says the Kings Indian approach is black's safest. Or so I'm told.

I know an expert that likes that opening

I would agree with you FirebrandX on the B4 opening.  It's only value in non-GM tournament play is shock value.  If White opens with this move and black is on his toes, Black would completely overwhelm the center.  While it allows White to Fianchetto his Bishop to B2 quickly, white must also spend needless time defending the B pawn.  (With Black's reply of E5, the B pawn immediately comes under attack and must be defended with a tempo or lose it.)  In addition White must spend another tempo moving the d pawn sooner or later or his middle game will be cramped.

Frankly, under tournament conditions, my opponents would laugh at me under their breath if I played this opening move.

ps FirebrandX, the chess game you listed to show Black's best reply to B4 I think is not that impressive.  White loses the B pawn in exchange for Black's E pawn!  Not good!

The great Aliechin once said that the Sokolski opening is  positionally and tactically sound, but that 1.b4 just declares its intentions too early (I would add, it is too 'one-sided'), so that Black can adapt to any further events easily.

At the amateur level I've noticed White often doesn't know the proper response to 1...c6 and I've gotten them to play 4. c3?! after 2. Bb2 Qb6  3. a3 a5.  Instead 4. c4 is correct because of 4...axb4  5. c5 and if 5...Qxc5??  6. axb4.  The position is still perfectably playable for Black though after 5...Qc7.  

This line is one of those recommended in Palliser's "Beating Unusual Chess Openings" and has the advantage of potentially surprising the surpriser.  However you must also be aware of an interesting gambit with 4. Nc3!? i.e. 4...axb4?! (instead 4....d5 or 4...Nf6)  5. axb4 Rxa1  6. Qxa1 Qxb4  7. Na4 with numerous threats.