Ugh, I wish this existed before I went to build a simpler extension to help remember my Facebook friends better! (http://trybackstory.com - shameless plug)

It's great that you support all the social sites - it was enough work for me just to integrate private notes and tags into Facebook. If only I had put in more time into Backstory to turn it from a side project into a full-fledged product like yours!

One thing I don't like is how intrusive the sidebar integrations are. They take up so much space that I can no longer see the other content in the sidebar at first glance. The Messenger integration also doesn't seem to be working for me.

Congrats on launch! I'm going to start using Dex, hope it helps me keep up with friends in the next few weeks! :)