Defending against early Bxf7+

Everyone knows f7 is a weak pawn from the get-go: scholar's mate hinges on its unique indefensibility.  But I've played several games where I've quickly lost the pawn due to some sort of sacrifice or trade.  The N+B for R+P exchange is another common example, which at least provides an even material exchange:

I often find that without the cover of f7 pawn, my castled K is at a disadvantage - vulnerable to diagonal threats by the Q, for example, or other things getting pinned in place because the K isn't in a safe location.

So my question is basically this:

Do you have any general tips for defending a position in which the f7 pawn is lost?  In particular, what "traps" or common attack strategies should I be aware of that the missing f7 pawn would allow my opponent to exploit?

Great question! (Obviously I can't answer it). Can someone clear this up?

There was a thread on this earlier http://www.chess.com/forum/view/chess-openings/ridiculous-opening-sacrifice

But I think the general advice is be happy that they are throwing away pieces and get the king to safety as soon as possible. But you probably knew that...

In the second example black also has a fairly decent advantage and it shouldn't be too hard to just put the king back on g8.

Nakanov: Uh... how exactly would you "not lose your f7 pawn" in the first example there?

Scottrf: Yeah, exactly.  It's not so much that the sacrifice is "unsound" or the N+B = R+P trade is "not really worth it", I already know that.  But like the commenter in the other post said - I end up spending a bunch of time defending myself and getting back to safety after such a sequence.

It's a bit of a white-knuckle experience the rest of the game because I don't know enough of what to expect White to pull next.  Hence, my post: what is White planning?!

Yeah, you can't go out of your way to stop your opponent doing something which is good for you.

In your first example though, white has no checks afterwards, you should have time to get the bishop out and 'castle by hand'.

...You still lose the f7 pawn.

Even if I do manage to castle manually - which is what I usually shoot for - aren't I at some risk from a light-squared diagonal attack from the Q?  Is h6 still a good idea?  In short, what White attack plan should I be prepared for?

These are the kind of questions I'm wondering about.

What is your problem exactly with these? You showed 2 positions, which are definietely better for white, in the first you just got a piece, white has no compensation for it. Your usual plan is to castle by hand in that position, for example:

And now the other.

Give us some concrete lines, if you still have problem with it.

Yes... those were sequences I gave to help illustrate what I was talking about.  I know they are bad sacrifices, I was merely using them to illustrate basic positions, not real-world examples.

I think you hit on it with this:

"And pawn does not matter if it has not got any function."

Perhaps my problem is that I am overestimating the value of f7 pawn, after I have castled Kside - but in realiy it is really not nearly so useful, especially when White lacks a light-squared B?

EDIT: What about a situation that doesn't cost White the light-squared B?  Like, say:

In other words, White retains a light-squared B free that can cover the diagonal originally blocked by f7.  Is this somewhat more dangerous, especially with f7 gone?

"Perhaps my problem is that I am overestimating the value of f7 pawn, after I have castled Kside - but in realiy it is really not nearly so useful, especially when White lacks a light-squared B?"

I wrote that for B+P in numbers are equal with K+N, but in practice, it is better to have the two piece. The f7 pawn is very important pawn, but you should not sacrifice piece for it, you should only if you can win something with that. So to sacrifice a piece on the f7 can be a good move as the move of a combination, but in itself it is not good to give a piece, or give 2 pieces for take the f7 pawn, even if you get f7 pawn + a rook. When you give K+B for f7 pawn + Rook, then you wont have light square bishop, but your opponent will have, so you dont have any advantage of there is no f7 pawn is a castled position.

The other example looks more interesting.

So all in all, if you sacrifice the light square bishop for the f7 pawn (and it is not the part of a combination, so just in itself) then you wont have any advantage, you will be in material disadvantage, and you wont be able to attack the king by the f7 square, because you wont have light square bishop, but the opponent will have, so it wont be a weakness. Even if you sacrifice knight instead of bishop, then your opponent still will have the light square bishop, so he can control the same squares, as you. So in it self, to sacrifice a piece for the f7 pawn is bad.

In the second example white traded off his only developed pieces. 

Let me summarize then:

* If you are castled (or manual-castled) Kingside, and you lose your f7 pawn, then an attack on the light squares becomes a possible threat - either through pins / skewers across the diagonal, or forcing the K into the h8 corner, where he might get hit by something else

* But you're pretty well secure from that if:

  - Your opponent doesn't have a light-squared bishop, or

  - Your opponent does, but you have one too, so you can cover the same squares.

Maybe consider trying to force a Q trade as well, to really disarm the opponent?

This forum is very helpful, I too feel my defense has been infiltrated so early in the game. 

Regarding early f7 sacs, White is typically playing for something like Fried Liver Attack or the Lolli Attack.  Rarely will you see an f7 sacrifice without any plan to continue the attack like in some of these diagrams.  This means the fastest way to take f7 isn't the most likely scenario, because White still has to justify the sac to himself.

Defensively, if you're that concerned over f7, I think playing e6, Nf6, g6, Bg7, O-O is good enough to force White into a different strategy.  

Nf6 protects the f7 pawn from the front, and e6 + g6 protects it from its diagonals.  Meanwhile fianchettoing the king's bishop and castling should give you a nice lead in development, should White move an already developed piece, if for lack of a plan B.