Some will say that 2% to 8% is the ideal density of keywords for SEO purposes. Others claim that optimum density for Google is specifically 2% and that anything higher will result in your site being penalized. For Yahoo and MSN, they specify a 5% keyword density. But is it really?
In my experience as an SEO writer, most internet marketers require keyword seeding density at 10% or higher. Now, if Google, which happens to be the most popular search engine in the internet, does indeed penalize websites with keywords seeded at more than 2%, don't you think that it's senseless for my clients to ask for more than 2% seeding?