Sometimes you're not quite sure which tags would be best for a question, especially on a site you don't use often.
Sometimes you know some words which could be tags but don't exist as tags and you can't always think of all the synonyms. Sometimes tags have names that are not easy to guess, for instance tags with abbreviations, jargon, or codes.
But often you can find questions of the same kind by doing a search because of common keywords which are not tags.
Well, why not enhance the "Search Results" functionality to sum up all the tags in the found questions, possibly summing up a greater number of questions than displayed on-screen, to produce a "Related Tags" module in the sidebar just like the one you get when looking at the page of an individual tag?