However, if you look at Technorati or (surprisingly) Google Blog Search, you do get different results. Technorati somewhat mitigates that by showing related tags. Google Blog Search I presume puts more emphasis on blog content than tags, which I guess can help explain the different results.

At the end of the day, I guess tagging still comes down to personal preference. For me, I prefer a more concise tag cloud, and thus I like to just pick one tag variant and stick with it. To me, yes - tags definitely have their SEO value, but more importantly, their primary function should be to help readers search for the right content they are looking for *after they arrive at your site*.

Therefore, I rather have a cleaner tag cloud to give users a better user experience, even if it means I miss out on some search traffic.

For rule #6, the rationale is basically to keep the tags as succinct as possible. Ideally, I want to avoid repeated words across different tags. Imagine if my blog is about enterprise software. If I don’t strip out vendor names in products, I will soon have tags such as “microsoft exchange”, “microsoft outlook”, “microsoft office” and so forth. Not to mention the mandatory “microsoft” tag which I need to distinguish between content between Microsoft and IBM, for example. That’s an awful lot of “microsoft” in the tag cloud, don’t you think?

From an SEO perspective, having one tag of “ibm lotus notes” should be similar in search performance to tagging each word separately. However, if you break up the tag phrase into shorter word tags, the added benefit is that should your readers search on just the tag “lotus” in Technorati or Google, the chances of your post appearing should also be much higher than if you tag it with the full phrase “ibm lotus notes”.

As for rule #9 - I generally want to use as few tags as necessary to describe the blog entry, and the plural base form of the noun sounds the most natural to me. Let me try to illustrate: When I tag something, I am basically filing it in a particular category or group. Now what sounds more natural to you in spoken English?

“This tag represents a group of shirts”, or “this tag represents a group of shirt”?

Search engines in general treat the plural and singular forms of search terms as the same, so this is entirely a personal choice. Same goes for “blogging” vs. “blogs”. In fact, do a Google search twice - once on the term “blogging”, and once on the term “blogs”. Notice that the results you get are more or less identical?

Also regarding #9, why choose “blogs” over the other terms? why not just tag all the terms? I must admit I’m not sure how these may or may not be picked up by searches, so would love to know more =)