the automatic-tags thing on vb.org is just crap. it use the thread title to generate tags. logically this is pointless, and even google is against the idea. it bring nothing to the meta search, it bring no real resumé of your thread, and it is not bringing real tags anyway.
My idea is different, when you create your thread, once it is posted you can see the Tags area in the bottom of the page — usual process… the difference come by the script i will post soon.
In the same path than tagthe.net – Webservice that tags your resources the little tool would simply be a little button in the « Edit Tags » field, and it would generate a list of tags depending on the thread title and first post content.
The logic will be the one of google keywords generator, using % of height in words to generate the most important keywords in the list and make them tags. It will not generate the list officially, but will just add the results in the « Add Tags » field, seperated by commas. The user can then choose the ones to keep.
The engine coded (in OOP) will be reusable in a cronjob, if you want, to force per-forum the generation of X tags per threads that do not have a tag stored.