Functionality Questions: Campaigns

Does the Sugar application have to be on a DMZ for URL Tracking and subscribe/unsubscribe?

What kind of additional load do Sugar servers can we expect by using Campaigns for marketing emails?

Does anyone have good/bad/evil experiences to share about the use of Campaigns?

And what is the future of the Campaigns module? When is it going Sidecar, and is it changing in any significant way?

thanks!

Francesca