There is nothing new under the sun, boys.
Ripping off other people's music is a long standing tradition in the music world. Mozart, Beethoven, Strauss... they all did it. It's a relatively recent thing for people to claim ownership of their music.
If you really want your head to explode, check this out:
We the Kings song: "Check Yes Juliet (Run Baby Run)"
Released February 4, 2008 on iTunes
Taylor Swift song: "Love Story"
Released September, 2008
Both in the same key. Very similar chord structure. Swift's chorus melody is nearly identical to the WtK verse. Both make heavy use of the "Romeo and Juliet" theme. Rip off? Hard to say, but it's VERY close.
End result? I cranked up my DAW and made a mashup. Kind of fun to hear Taylor Swift singing a punk rock song. :-)