Your Ezine-Engine account helps you understand which of your list building efforts are working.
If you're serious about building your list, you'll want to know which of your promotions are working.
If you know where your subscribers are coming from you can:

Focus your energy and ad buys on those promotion strategies that are working the best, and...
Stop wasting time and money on efforts that aren't generating sign ups.
If flying blind isn't your thing, you'll be happy to know your Ezine-Engine can track new subscribers from the ad click, to your site, and on to your mailing list.
Your account will keep a record of how many subscribers each ad is generating, and present you with a simple display that shows at a glance which of your promotion campaigns are generating the most subscribers.
Here's How It Works
We all know we're supposed to be tracking our ads, but often we don't because it just seems like too much bother.
Using your Ezine-Engine account, you can set up tracking for one of your ads in just a few clicks.
All you do is:
1) Login to your account, and choose a tracking code for your ad. Any single word will work.
2) Then, add a ? and your tracking code to the end of your the URL in your ad.
That's it. Your account will now automatically count every subscriber that follows that ad to your signup form.
You can set up as many tracking codes as you need.
Examples
Are you posting in forums, and hoping that readers will click on the link in your signature, and then signup to your newsletter? Stop guessing whether all this posting is worth your time. Add a tracking code to your forum signature URL, and you'll know for sure.

Are you buying Adwords ads? Do you want to know how much you're paying per subscriber? Add a tracking code to your Adword ad, and find out.
Are you promoting your newsletter in your email signature? Are recipients reading your sig? A tracking code can tell you.
Do you want to split test your sign up pages against one another until you find the very best sales copy? You'll need to know how many subscribers each page is generating, and tracking codes will give you that information.
You get the idea. Your Ezine-Engine account will help you target your efforts at the most productive and cost effective list building strategies.