Where are you hiding your opt-in?
I subscriber to a lot of email, and frequently I’m reading a marketers RSS feed (almost 100 at last count) published by the same company as well. I’m often surprised by some marketers or sites that don’t have a clear or easy to find a subscription mechanism. If I want information from you, make it easy to find – you may be surprised at the list growth you experience.
This also goes for your RSS feeds, making this easy to subscribe to should be part of your design and execution processes, hiding these or not providing them could be costing you valuable subscribers. Feedburner makes it very easy to add various subscription services directly to your page with their “Chicklet Chooser”, making it easy for users to add to their Yahoo page, or their Google reader.
For example you will notice the EmailKarma subscription box is easily found to the right side of the page, and the choice for both email and RSS are available, making it easy and obvious to access by you the reader. I also employ a double opt-in to ensure that you really are you when subscribing.
Interested users should be given easy methods to interact and access relevant information on your site, in your RSS feed or via your email program. Have at least one subscription form on every page make sure it is above the fold and easy to understand for all of these options.