As well as being an intentional alternative to the word fuck, people with extremely noticable California accents say the word "fuck" in a way that comes out more like "feck."
Oh feck, man, the waves are like totally non-surfable today dude.
Alternative to fuck, used not entirely by do-gooders who want to avoid the foulest four letter word, but mainly by internet users humorously trying to imitate them.