I understand your concern, but I am not sure that having separate tags for tablet, iPad, and ipad2 would necessarily be a problem. Someone might be interested

I understand your concern, but I am not sure that having separate tags for tablet, iPad, and ipad2 would necessarily be a problem. Someone might be interested in tablets in general, but wouldn't want to see stories on the ipad. On the other hand, ipad2 is clearly a subcategory of ipad. And someone who is interested in the ipad will probably be interested in stories about the ipad2, even though he may not have explicitly looked for ipad2 tags but only for ipad tags. Since "ipad" is actually a substring of "ipad2", this could be easily solved with a simple substring search in the tag. A more problematic example is someone missing a story tagged "java" but not "programming" when searching for stories tagged "programming". The solution to this problem is to have a tag hierarchy. Thus, the "java" tag would be explicitly made a subtag of the "programming" tag. Unfortunately, the problem with this solution is that it's not easily automatable (though I'm sure there's been a lot of research done in this area), so the hierarchy would probably have to be built by hand. And this, in turn, means that it probably won't be done for a lot of tags. Perhaps a good compromise would be to require each story to be tagged with at least one predefined tag (from a wide selection of predefined tags that are already organized in to a tag hierarchy), and allow an arbitrary number of user-defined tags. That way there'll be at least some minimal organization to the submitted stories.