The word ‘foul’ (offensive, noxious, unfair) could often apply to that which is ‘fell’ (fierce, ruthless, terrible, deadly). The above example relating to the forced eviction of settlers in Gaza is such an example. This coincidence of meaning and the words’ similarity in sound combined the low awareness of the word ‘fell’ creates the ideal conditions for an eggcorn.
The Concise Oxford defines ‘at one fell swoop’ as ‘in a single (deadly) action’. Popular use of the phrase and the eggcorn often draws on the ’single action’ part of the meaning only. For example, deleting all items at once from your Microsoft Office clipboard is neither offensive nor deadly. Though it can be done in one single action this swoop would be neither foul nor fell. Hence either meaning is equally [in]appropriate. The same applies to the Between The Lines example.
The Guardian Unlimited book reviewer in another example above may have quite knowingly used the eggcorn because the word foul is so appropriate in the context of a kiss and tell biography.
Media Monitors’ A Case for Ethics talks about ‘a dirty deed’ thus underlining the new meaning of the eggcorn.
In a somewhat self-referencing example, the Christian Times writer used written words improperly and thus partially destroyed some of his own good work.
See also fell»fowl.
[CW, 2005/08/29: marked as “questionable”. The substitution certainly involves a semantic reinterpretation, but phonetically, the distance between _fell_ and _foul_ is rather a stretch.]