I think the MIME Type should get priority in determining 
the 'true type' of the file.  It'll help solve the cases 
of .ASP/.CGI/.PL URL extensions.

I would say that in the case of foo.com/cgi.exe, if coupled 
with MIME-type text/html, that it should be checked for 
the '404' error strings I mention in my previous post.  
These 'binary' types should also be checked by default if 
they were associated with MIME-type text/html: 
+*.gif +*.jpg +*.png +*.tif +*.bmp
+*.zip +*.tar +*.tgz +*.gz +*.rar +*.z +*.exe
+*.mov +*.mpg +*.mpeg +*.avi +*.asf +*.mp3 +*.mp2 +*.rm 
+*.wav +*.vob +*.qt +*.vid +*.ac3

Ideally it would be possible to add other binary types and 
override the defaults.

I think the case of a .exe named cgi returning a page with 
the 404 trigger strings in it is more unlikely than finding 
an actual .exe file to download.

Phew...this problem is not simple at all...