Internet traffic sources: a personal experiment

I wrote in a previous post about the importance of social bookmarking sites and how they add a significant number of page views to a site. It is true, but now, after one month of more research, I discovered that search engines are not at all to be disregarded when building traffic and that the best practise would be a combination of all promotion means.

Premises of my research:

For three weeks, I posted at least once a day and I submitted all articles to some 5-6 of the most important social bookmarking sites
Over the last 4 days of the experiment, I did not post anything new
I paid some attention to keywords (I chose about two or three per page and I made sure they can be found in the first part of the text), but I did not try to optimize my pages for search engines
My site ranks amongst the first 30 only in one search engine and only for one keyword

Results:

after each submission to social bookmarking sites, I noticed an increase in traffic of about 80%
the next day after each submission, the traffic remained higher than in the previous day (some 30%)
after not submitting anything for 4 days, the traffic dropped to 1/3, while the number of clicks on ads remained constant
30% of all page views in the last 4 days came from search engines

Conclusions:

the most part of ads conversions seem to be coming from people who search for a particular topic
search engines can bring in a significant traffic, so SEO is definitely not a waste of time
social bookmarking submissions are also good, because they generate traffic on the spot and in the same time, each submission ads some permanent traffic to the site
Additionally, I noticed another positive phenomenon: despite the fact that I did not perform any SEO, my site was listed on the first page in some engines because of the submissions I did to social bookmarking sites (actually, the SE showed the page of that social bookmarking site that displayed my submission).