Is it clever to use tags for a blog (or a website) for SEO?
The listing of a resource in the form of tags (non-collaborative folksonomy for a blog) has become very popular since the advent of the famous "Web 2.0".
As a consequence, we have seen tags and even 2D or 3D tags clouds blooming on many blogs and online services.
Since the user interest goes beyond this scope, let's focus on the impact on search engines.
Listing pages generated by tags sometimes duplicate pages like "category", for example.
When we start a new website, few of our articles are tagged and plenty of pages with a very similar and poor content are potentially created.
The massive use of tags (and even more so of clouds) can lead to a strong increase in the volume of links per page. It will be then important to keep a close eye on this data, as well as on the ratio single text / links per page.
As you already got it, tags must be used with great caution. This is not a miraculous solution.
Moreover, tags pages are often devoid of their own content. In addition to considerably increasing the number of links (and thus decreasing the weight of each of these internal links), they also generate duplicate content within the website itself.
However, some page tags sometimes rank very well on search engines.
This behavior reminds us of the importance of internal linking which sometimes plays a crucial role on large websites.Still, be careful! You should not give search engines too many empty (or almost empty) and repetitive pages.