because I want to know precisely which pages my visitors are intereted in.
Your visitors are interested in the pages that come up highest in your stats. (I'm necessarily simplifying here, but generally.) Finding that out doesn't require disappearing everything you assume is not interesting.
Let's say for the sake of discussion that your tag page for the topic "seo" becomes a useful reference that people share and can be scanned for interesting posts. What you're proposing will actively block search engines from seeing that page and also sending people there.
If the visitor found a tag archive through the search engine, which displays many posts in one go, I won't know which post the visitor is interested in just by looking at the stats.
- This is only true if your tag/category/etc. archives show the full post content. This is generally not the case to start with.
- If it is the case with your particular template, it probably makes more sense for you to change it so excerpts are shown rather than block engines from accessing the rest of your site.
- You're only thinking about search engines in your question, which is often a good sign of a bad idea. If someone happens to reach one of those listing pages by just navigating the site, you're still not going to be able to tell why they were there, either. Again: that's what your stats are for.
So to achieve this I should add "follow, [no]index" to tag/category/author/date archive pages.
- The noindex value will cause the listing page to not be indexed by search engines. It's ultimately your decision whether you want to do that, but I see no good reason for it given the reasoning you've provided.
- There's no such thing as rel="follow" Just leave it off. Follow is the default behavior.
Would this have bad side-effects?
It would have some effects I don't know that you've considered(eg. what I said about your tag page being a reference). I'm not sure it would have any explicitly bad effects in terms of search engines, though it will make it so that your site is "smaller" as far as search engines and their results are concerned.