Ankh - actually, no.
The only people who are absolved from blame for re-posting a thread that has exactly been done before are people who meet both criteria:
a) are newbies who weren't around when the thread was done.
b) if the thread wasn't within the past month or 2 (meaning that if someone IS new, they should read back at least 3 pages before starting a new thread)
c) they aren't a Community Supporter (i.e. they can't search).
If all 3 of those are passed, then what should happen is that the first Community Supporter that reads the re-thread should post a quick link to the thread which discussed the same exact subject, and then the re-thread should be closed.
That's what's done on other boards, so I don't see why that's a pipe dream.