Blogs are increasing in popularity as an easy to promote website. Blogs tend to have better search engine visibility and rankings and they have many advantages over conventional websites.
Each blog post is worth a few backlinks straight off the bat. This is because each time you post your blog software pings services like technorati which then link to your post. The more you post the more backlinks you get and the greater your chances of higher page rank.
Blogs also seem to have more “pages” of content than static websites. Consider in how many ways a single post appears. It can be accessed through your frontpage, archives, category overview, tag overview or as a single post. In almost every case it appears alongside different posts that together make the whole page unique. This is why blogs have more pages and SEs like websites with lots of pages.
By its very nature a blog is designed to be updated regularly. SEs love websites that have fresh content and so they will rank a blog with regularly updated content better than a static site that is only occassionaly updated.
Blogs are also easier to promote because they provided rss feeds that your users can subscribe to.
One of the most important factors behind SEO is the need to have your content at the very start of your web page. Since a lot of blogs favour the right hand sidebar, they usually have most of their content at the beginning of the source code. This makes them more search engine friendly.
For all these reasons blogs are easier to promote.