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My main worry would be that spammers start to use the method you're describing en masse. This might cause a reduction in search quality and a lot of complaints. About a year ago, heavy cross-linking of domains was seen in this light and we know that the penalties were also triggered by people who cross-linked for legitimate purposes. This, in my opinion, suggests some potential for danger in the future.
Personally, I wouldn't rely too heavily on <noframes> content either (although some people report no problems getting it ranked well).