If there's anything about Sifter that I have a love-hate relationship with, it's managing feature requests. On one hand, feature requests and customer feedback are the most valuable ways of understanding where we should steer the ship, and the people that take the time to share are priceless. On the other hand, some people request features with the entitlement of spoiled children who have never heard the word "no" in their lives.
http://nextupdate.com/blog/archives/2009/04/managing-feature-requests/We'll only send emails for significant product announcements, and those happen every couple of months at most. Of course, we won't give away or sell your e-mail address either.