Hmm... looking into tagging - does anyone think it's used much?

Particularly in a non-blog but information packed environment - do you think it increases deep viewing into a website?

Any research - I read a bit - about 2 years old says - somethign like 70% of people don't tag - nonetheless I think people do click on say most popular tags etc (from a cloud etc)

Any thoughts any experience - can you show me site where tagging is used (by the actual users / visitors).

Thanks - I know very little about this - not a tagger myself - hmm are you? - any thoughts at all would be great