When you go to someone's profile and you're connected to them, there's a section called "Relationship". On there you can add tags, notes, or reminders. That's what I'm talking about.

I think you're using tags, but notes are also a great way to annotate contacts.

Again, I personally don't use these features that much, but I just wanted to point out that they do exist and people can probably get some significant value out of them. Perhaps part of it is a discover problem?