Could it be harmful to over-optimize a Web page?

Contradiction

Taking the question literally, building too many links to your site, particularly if it's new, can cause it to drop or dance longer than it would otherwise.

If Google wants to make an example of you (ala JC Penney), your rankings will be manually forced down until you clean up your site. But that's highly unlikely unless you're a huge brand and it gets SEO industry attention :p

Aside from these rare examples, Google tends to penalise sites that sell links rather than sites who buy them.

SO TRUE

I recently did a test with over 100.000 scrapebox/xrumer backlinks on a 1 month old domain that had 40 unique visitors a day. My site started to dance a little for less then a week and my visitors dropped a bit, but within the same week the site stabilized and the visitors came back to around 40/day.

To make things worse, the site I tested this on was a thin affiliate site with spun content. (7500 pages indexed)

By definition you can't over optimize...

Use your noggins folks.

Hi privatenetwork,

By definition, you cannot over-optimize, that is a nonsensical notion.

Optimization is the process of finding the optimal ratio of keyword content. You cannot go beyond optimal, only fall short of it.

What you seem to be asking is if you can go overboard on link building, which isn't in and of itself optimization, it is promotional link building. Optimization is the act of including relevancy signals in an optimal fashion within content you are creating.

To answer the question you seem to be asking, I would say no, absolutely not possible to go overboard on link building if you are following Google's guidelines. However, many folks have the wrong idea about what is acceptable content and doing even a little bit of spamming is not good. The more you do the worse of a nuisance you become. So if you are asking if you can go overboard in creating web spam, why yes, you can. So don't do it, not even a little bit.