Soft Pins are Presumptuous
Beware presuming too much. A soft Pin is just that...soft. Often times players make the mistake of thinking a soft Pin is absolute. Only a hard Pin is absolute. What's the difference? A hard Pin is when a piece is Pinned against the King. By rule that piece cannot move (placing its King in check by moving out of the line of fire). A soft Pin is when a piece is Pinned against a valuable piece (like a Queen). A common example of a soft Pin is when Black Pins the White Knight on f3 against its Queen by placing the Blacks light squared Bishop on g4. If you've been playing chess for any length of time you have no doubt either used this Pin or had it used against you.
Unfortunately, many of us assume that this Pin is rock solid because who in their right mind would move the Knight allowing Black to trade their Bishop for a Queen?!
While reading through a couple books I found some intriguing examples of Black getting abused for presuming the soft Pin was more powerful that it really is.
My favorite example is found in The Art of Attack in Chess by Vladimir Vukovic. He sites a game played by Legall vs St-Brie in Paris 1750:
Understanding fundamental concepts such as these will propel your game to the next level. Be careful not to assume your pin is stronger than it is.
Here is an example from one of my own games. I just captured my opponents Knight on e4 relieving him from his position in a strong outpost. I assumed my opponent would recapture with his pawn...but as we'll see he attempts to get me locked into a cross pin. By capturing a pawn with his Rook you'll see that I can't recapture with my pawn as it is pinned to my Queen, and now my Bishop is also pinned to the Queen...what to do? Recognize the pin is soft and give a discovered attack with check...the Rook is mine.
I hope these examples make you more aware of the soft Pins potential weakness.