I just got a note today that zvents had implemented our Address Book Access widget, so I navigated over there and indeed they have!
When you’re on an event page, just look for the “Email this event to a friend” link. From there, you can launch our widget to quickly grab your friends’ e-mail addresses and share the event page with them. A quick timesaver we hope 
We’ve seen some pretty good response towards our widget; more and more people are signing up to use it everyday. Hey, why build Yahoo, Hotmail, GMail, and Outlook import when Plaxo’s already done it for you? If you’re interested in the widget, or have questions about it, feel free to e-mail me.
– Mark Jen, Product Manager
Update: Looks like they’ve mentioned it on their blog as well
