In the mid-1960s, I was first taught to love the native Blues music of America by five Englishmen who gave these blues their own guitar-and-harmonica driven spin...the Yardbirds. Keith Relf, Jim McCarty, Chris Dreja and Eric Clapton cranked For Your Love into the airwaves of my hometown, and everything seemed to change. Later Clapton would leave to be replaced by Jeff Beck, and Jimmy Page joined on bass. Through this period, the band mingled updated classic blues like Smokestack Lightnin with newer proto-psychedelic material like Shapes of Things, but credited the blues material, as did the Stones, Beatles, and other British pop-blues groups, to the original composers.
When Page gained ascendancy in the band, things began to change. In other words, lyrics, titles, guitar parts, entire songs were lifted from their underpriveledged composers and ascribed to Page/Plant/Jones/Bonham. Page didn't restrict his theft to the old timers of the blues, however. He consistently stole concepts, techniques and songs from his former bandmates and from other bands that he toured with. Dazed and Confused was the work of a blues artist Page saw in New York. The Yardbirds covered this song live for several years before it emerged on Led Zepplin as an "original" composition. He sued to keep a pre-1968 Yardbirds version from being released. The entire acoustic intro to Stairway to Heaven was stolen from Spirit's Taurus after Zeppelin toured with them.
If you are interested in Page, Zeppelin, the Yardbirds, or rampant acts of plagiarism, see this article. Really pretty entertaining stuff.