Facebook announced a few new features last week, as well as updates about its profitability and prototypes.

But for us, @tagging remains the most interesting development (and we wrote about tagging metrics last week as a result).

We’re wondering how users outside the tech community will learn about and understand @tagging. We’ve found one clue that happens when you mouseover a tagged item- a small box that explains the system.

We may have missed the notice, but outside of the Facebook blog, this is the only notification of @Tagging we’ve seen. It looks like Facebook wants this product to spread virally and unobtrusively. The interesting thing will be to see if it actually does.