Like adeptus said, why do you really want it? There isn't a real advantage here. I can imagine re-writing URLs like
http://www.asip.be/forum/index.php?topic=17.msg58#new to
http://www.asip.be/forum/17-topic-title/58#new or something which will give an advantage at searchengines and doesn't piss of your visitors, but cloaking is a different thing.
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