Everytime you select a category, tag, archive or post from a list you are indicating a preference, but blogs aren’t yet making use of these indicators and I think it is time they did.
When you find a new blog you often end up navigating through it to see what else is on offer, but that is a fairly random process. You might not be searching for anything in-particular but your habits will certainly indicated your interests and there are ways for blogs to use that to your advantage.
If, after reading the first post, you click on an archive to read more then you are indicating that something about the initial post was probably interesting enough to make you want more.
If you select a category or a tag then you are expressing an interest in that topic, and if you select a post from a list then you are expressing an interest in the topics represented in the title or excerpt of that post.
By tracking your movement through the blog and adding each choice to a profile the blog can begin to identify which posts are more likely to interest you and promote them to the top of lists.
Knowing which posts you have already read also helps to keep the suggestions fresh.
Would you like to see blogs that anticipate your interests? or would you rather just browse and hope?