If you'll forgive me my lack of time today, I'd like to link you to a New York Times examination of the case, Skyhook Wireless v. Google (or as I like to call it, the "Jabbar" case). The reason I'm singling this out is, if you follow the story, you'll see a great example of how seemingly innocuous statements contained in email messages, laid end-to-end, balloon into something much bigger.
Oh, and if somebody sends you an email – and you feel it would be more appropriate to continue the discussion off-line – walk by their office (if possible) or pick up the phone. Don't email them back, "PLEASE DO NOT! Thread-kill and talk to me off-line with any questions".
If I saw that in document review, where do you think I'd start digging?