I have noticed some posts referring to the googlebot marking a site for spamming ... the only spamming I know of is through email. Anyone care to enlighten me on what this is and how it may affect me or others who are trying to optimize our sites? What should I not do to avoid being 'marked'?

This is a odd area that you apporaching, their isn't a huge amount of agreement to what is spamming.

The only one that people seem to all agree on (que for someone to disagree with me) is hidden text. This is when you have text that is the same color as the background so that it does appear visible, but count for search engines. This is also something that search engine would have much trouble identifying.

Apart from that the jury is still out as far as I know, many other things some people consider spamming like cloaking and doorway pages but these all can have perfectly practical uses. One of the think that some people are talking about as well is un-natural linking, but their is nothing solid on that either.