Somewhere in the middle of the SmartTags fray, there was a story quoting a lawyer that claimed that adding the Smart Tag disallow metatag could be a problem. The theory was that adding the MS tag could enable MS to claim you page was a derivative work.
It is different than adding other types of code such as affiliate code or banner code, since it is designed to go into the head section of your document - which does nothing but describe your page. There were parts of that argument used in the famous Metatag trials and in the Playboy vs Excite trial.
Anyone know where that article is that quote the lawyer on the derivative workds comment is at? I can't seem to locate it.