[cd34]

###HOTLINKING BEGIN
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://thissite.com [NC]
RewriteCond %{HTTP_REFERER} !^http://www.thissite.com [NC]
RewriteCond %{HTTP_REFERER} !^http://othersite.com [NC]
RewriteCond %{HTTP_REFERER} !^http://www.othersite.com [NC]
!^http://1.2.345.678.9[NC]
RewriteRule .*\.([Jj][Pp][Gg]|[Gg][Ii][Ff])$ http://www.someplacetoredirect404.c...EMOVE/NO_NO.gif  [R,L]
###HOTLINKING END

First, you don't need the .*$ at the end, that requires an end of line match anchor which just wastes regexp processing. Even with your existing rules, your first rule would have also matched your third rule with the :80.*

Fewer rules = better, however, there are certain regexp rules that take more processing than chained rules.

anchored matches are always better