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brotherhood_of_LAN - 5:13 pm on Apr 14, 2010 (gmt 0)
I think one of the problems is that search engines finding cloaking agreeable would then be asked to provide a list of IPs that they spider from, further encouraging cloaking.
You would then have a raft of people complaining that their site got kicked because they were using cloaking in what the search engines perceive as "unsavoury".
It's always been a contentious area, it seems SE's say "don't cloak" to err on the safer side of things.