One of the things that many SEO experts recommend when building a site with optimization in mind is to refrain from "keyword stuffing". This involves dropping a large number of keywords, often duplicated, in the keyword META Tag. I've found that it isn't the case that keyword stuffing is a detrimental thing in all instances.
Many of the websites I build and manage are for local companies that are targeting a local client base. For example, I built a site for an electrical contractor in my local area. He doesn't want work in Florida or New York; he only desires inquiries from local residents and/or businesses. When building his site, I chose a domain name with his keywords, then I stuffed the heck out of the keyword META tag. I didn't use the exact same keyword many times, but I used hundreds of variations in it. I wasn't sure how this would affect his rankings. Here's what I found:
- The electrical contractor's site was ranked in the top ten in both Yahoo and MSN in less than a week for ALL the major keywords. This was several months ago, and he remains near the top, bouncing between #3 and #6 on both Yahoo and MSN.
- Google, at first, wouldn't touch the site, and only indexed the home page.
- After several months, the website slowly started moving up the SERP rankings in Google, and is now in the top 20. This is WITH the stuffed keyword META tag still in place.
- The site is ranked #1 in Google for one of the more obscure keywords, and I expect that some of the more competitive keywords will rank in the top 10 soon.
Conclusion: while the stuffed keywords seemed to anger the Google gods at first, eventually the age of the domain overcame that and the site started to move up the rankings. Yahoo and MSN don't seem to care about keyword stuffing, and in fact ranked the site highly even in it's infancy.
I wouldn't recommend trying this on a site that you require high rankings for, but if you have a site that doesn't require any SEO, give it a test and see if your conclusions are the same.