[buro9]

Have you checked whether it adds load?

I don't think it does. The SQL side of things is pretty lean (though adding an index on the 'tag' column of the zoints_tags table will help fractionally), there are only 17 queries on my tag pages, a standard forum page has 15. And an explain of the page shows that the SQL is taking less time to run than that on a standard forum listing.

There is a lot more work in the PHP though, possibly room for optimisation there. But it's fractional and you'd gain very little for a lot of effort.

For an idea of this:
A standard forum display page:
Page generated in 0.25203 seconds with 15 queries
A zoints tag page:
Page generated in 0.21700 seconds with 17 queries

Ignore the minor difference... the point is that the load is almost identical in terms of processing time, and the SQL doesn't tax the server at all.

You certainly could exclude guests from viewing tags, but I cannot think of a benefit from doing so. You'd also be preventing Google spiders from seeing the tags, and frankly the potential for tagging to improve your Page Rank is pretty good, because they provide more context to the threads and a URL in which the context is present.

Yes it's possible, but seriously think about why you would want to do it when performance isn't a strong argument to use.