Sometimes, I've been burned by remixes, particularly when a single hits the air, and it's the remixed version, but nobody says anything. The worst example I ever experienced was from The Fugees first album.
If you caught the video, or heard it on the radio, Vocab was a nice, mellow track. On the album, the tempo was different, the vibe was different - they sounded downright angry!
Warning: Explicit Lyrics and iTunes links. Here's what the radio and MTV were playing. Here's what you'd get on the album.