Android can now support OBEX file exchange over bluetooth.
 
For some reason I cannot quite fathom the developers have chosen to hard code a small list of mime types into the OBEX Android code.
 
So if you want to send plain text, or a .gif or .jpg image to your 2.1 based device (For example my Dell Streak), it works fine*.
 
But the Dell Streak comes with Quick Office, so let's say I want to send a M$ Word file (.doc) from my Desk Top machine to the Dell Streak -- Well it's a word file, and thus has a different mime type ("application/msword" or something like that), so the Android device arbitrarily rejects it.
 
The simple workaround is to simply rename the file before you send it.  Such as
 
document.doc   ==>  document.doc.txt
 
The desktop OS will then send it with a mime type appropriate for text, which Android is perfectly happy with.
 
Once it's on the Dell Streak, go to the file manager part of Quick Office (or other file manager) and rename it back to document.doc.
 
If the file is not surviving the transfer once you call it text, try a different fake extension, such as .jpg.
 
It's a good example of something that was probably done in the name of security, but really makes it harder for the user, while being extremely unlikely to stop anything nasty.
 
*(Note: Different devices support different BT profiles.  Some devices do not allow BT file transfer at all.)