[punaniman]

Linkster, I have heard the same thing. People seem to be concerned that it will be too easy to tell that a site is SEO'd by using that attribute, thus google will penalise the sites using it. I have not seen any real reasons other than this and the usual google paranoia.

I dont image that it would get penalised as google are the ones that initiated its use. Plus it is a great tool to stop forum and blog spam and thus is in the SE's best interest use it. Thus I can't see them having a problem with it.