Many people send and recieve documents in the proprietary .doc format by Microsoft. This is not good. Why not you ask? Well, it's not a standard. No, you say. But everyone uses Microsoft and probably uses Word...how can it not be a standard? For one not everybody uses Windows, and everybody who uses Windows doesn't use Word.

Word files are bad for even those who use Word. Different versions of word aren't compatible with each other. Documents look and print differently on different computers (even though they may be running the same version of windows and word)

Here are some links to help you:
http://www.nothingisreal.com/dfki/no-word
http://www.cse.unsw.edu.au/~chak/email.html
http://bcn.boulder.co.us/~neal/attachments.html
http://www.cs.uit.no/~tobias/NEW/word-rejection.html
http://www.gnu.org/philosophy/no-word-attachments.html