Existing users, 
This app seems to spam the addresses in your addressbook without your consent with this message:
From: Gizmo Project <noreply@gizmoproject.com>
Date: February 1, 2006 7:31:03 AM PST
To:you@yourisp.com
Subject: You've been invited to Gizmo Project
Reply-To: Gizmo Project <noreply@gizmoproject.com>, yourfriend@isp.com
Your friend, yourfriend@isp.com, wants to talk to you on Gizmo Project
Your friend, yourfriend@isp.com, wants to tell you: "Hey, check out this free new software that lets you talk for free. I am using it now."
Gizmo5
P2P telephony client using the SIP protocol
Version: 4.0.0.260
BE CAREFUL
Feedback Type: Usage Tip
Contributed by: Axel Thursday, February 02 2006 @ 12:11 PM PST
Product Platform: MacOSX
Used Product For: Have Not Tried
Recommend Product: NO
Comments
Nobody spamming anyone - Ilgaz
It is YOU using option "invite your contacts to gizmo" option, VIA YOUR COMPUTER.Friday, March 17 2006 @ 06:02 PM PST
BE CAREFUL - FallGuy7254
Actually, it does ask you if you want to import contacts from your address book and invite them to use Gizmo, but the wording is rather vague so many people miss it, like you apparently did.Reply to This
Thursday, March 16 2006 @ 09:15 AM PST