I read a great blog post from Dare Obasanjo that mentioned the effect of "people tagging" on Facebook's growth. People tagging being that nice feature of Facebook photos where you can draw a little rectangle around your friend's face and put their name to it. Your friend gets an email, clicks through to the Facebook photo, and gets to enjoy looking at their own drunken facial expressions.
When I started using Flickr a couple years ago and as a regular Facebook user I was shocked to find no "people tagging." My friend ceedub recommended picking a tag for myself, then telling all my friends to tag me with it in all their photos. Lame.
Another great use of people tagging is blog social networks like LiveJournal and Vox. I love writing a blog post and linking to all my friends mentioned in the post. Actually, I might build that feature into the next version of my leahculver.com blog ;)
I'm so sad that Pownce was really my first attempt at a consumer web product and that I didn't get much of a chance to iterate on its product design. I'm taking a bit of a break from making social apps right now, but I can't help but mull over the little things that really make the web feel like people party.