Understandably we all want our websites to rank well in a seach top 3 ideally but 1st page at worst.
Of course this should come second to content and usability, From an article i read a few months back, creating a site primarily for the seach engines will hurt your websites usability.
I will back this up with reference to the article when i find it again it was quite an interesting read, although im not huge on SEO at all, i simply consider that if im doing anything at all to help a search engine then they should be thankful, my concerns are for my visitors liking and visiting my site
A search engine really should not need us to plug our sites with keywords, the have the capability of figuring out what a page is all about, the main concern, say for blogging, keep on topic and keep it engaging. this goes for any website though.