If there’s a site that doesn’t display # of RSS subscribers, here’s a simple way to compare and spy:
1. Goto Google Reader and subscribe to the blog you wish to spy on.
2. Click on “show details” as shown below:
3. Google reader will tell you how many readers are subscribed via Google reader.
Now, this won’t tell you exactly how many are subscribed to the blog, but at least it will give you a good knowledge of how many in comparison to your blog. (For example, Zedomax.com actually gets about 1300 RSS subscribers but only 163 Google Reader users)