Internet Explorer 7 is launching, and two social services have impressed the team enough to be included as "Recommended Add-Ons". That could dramatically increase the number of users for both services, and really help them break into the mainstream.
But wait, there's more! Trailfire also has a web-based profile for every user that lets you explore the trails they've created. This element is very lightweight, however, and they might want to turn it into a full blown social network. In fact, users are sometimes unwilling to download yet more software, so offering more ways to explore the site without downloading the toolbar would be wise. It's theoretically possible that you could create a trail through the site without downloading any software - this is a feature I'd love to see.