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Detect if user is using Mozilla, Opera whatever.
If not, serve a text version of the site. No spam. Only difference is that the site is all text. I have no problem with the Google cache showing this. The "justification" is that the text site is there for non-graphical browsers such as Lynx.
I take it the search engines wouldn't approve?
Also since it's so visible a technique, if you are successful with it, you'll probably draw a lot of unwanted attention.