When I wrote my very first blog post, I didn't know much about SEO. I read a lot about search engine optimization from Grizz's blog about making money online. Grizz recommended spending 90% of your time on link-building whereas you spend 10% off your time actually on your site.
This is good if you are going for very competitive keywords but I find it far more effective to say include a keyword in the title of page for a site like increase stature(and stature increase) then to just build links to a site with all the variable long tails. In fact, if you actually include your keywords in the title(and at least once in the body) then you get the benefit of having those keywords being bold-ed in the search engine results which increases your click-thru rate.
Regardless of LSI(Latent Semantic Index), it is always better to have the exact keywords in the title you want to optimize(even to the degree of earn cash online versus earning cash online versus cash earning online). Article directory sites do not follow the 90/10 ratio and do very well for themselves. Although article directory sites do get "free" links from time to time from people wanting to either increase the link juice from the article or to increase the search engine ranking of the article itself, content creation plays a far more important role to article sites than does building back-links.
I explained more about this in my post about the power of content. To get the mega keywords like in my niche height increase, it's a great deal helpful to have the name of your site be height increase and to have lots of links pointing to your home page with the anchor text of height increase. According to broad match in Google Adwords tool, height increase is searched for over 200,000 times a month. In exact match, height increase is searched for only 9000 times for month. Add one part to that tail and guess where the exact matching domains rank? No where to be found. It even hurts if you flip the order of the words around ie. increase height versus height increase.
What do people do when they don't find what they're looking for? They add more keywords to what they're looking for.
The 50/50 system involves going after really long tails(keywords that aren't in google keywords tool). Each post is optimized for one specific keyword and you only send one or two links to the post with that keyword(you can make it even easier and send a blog comment link with just your name to that post). Targeting really long tails even if they're only searched for once or twice a month allows you to gradually build targeted traffic over time
If you're the only site on the page in the search engine results with the title bolded and the long tail keyword bolded, how do you think you're going to look to the searcher? You're going to look really good and the results with be an increased click-thru rate, more time on your site, and a lower bounce rate.