Seeing how many subscribers helps you know what type of reach you have, but a subscriber is just a number. As a person who has used a number of feed readers (Firefox Sage, Bloglines, FeedDemon, & Google Reader), and as a person who has over 100 blogs in his reader, I have come to realize that the number of subscribers does not matter much. Sometimes I read all 100 + blogs I subscribe to, but most of the time I just check out my favorite channels.
When new subscribers join that is great, but I think most people with feed readers do not cull their feeds often (based on personal experience and chatting with a few friends). Many subscribers may not be readers.
What really matters is the number of people who think your content is interesting enough to reference it. Blogs are viral, and your true reach is not your number of subscribers, but a combination of the following:
- the reach of your best subscribers
- how likely they are to help you spread your story
- how easy your story is to spread / how interesting your story is
Most competitive channels are going to have a few original voices and a bunch of echoing channels. So long as your blog is good enough to be considered one of the original channels, and so long as some of the other original channels occassionally reference your blog then that is all that matters.
You do not need to compete cross industry, you only need to be well known within your industry to gain exceptional exposure.
As far as the echo chamber effect goes, some of the echoing channels will be real people, and some of them will be driven by algorithms.
I tend to shy away from using FeedBurner or other similar products because I want people directly connecting to my site. That way, if some of the people are a bit lazy and link to a feed, or if some of the bots automatically link to a feed URL I still still want those links helping boost my overall site popularity score.
Bloglines will give you a number of subscribers there. It will only be a sample of your total subscribers, but unless you are selling direct ads in your feeds the exact number of readers does not matter much, and some of the best readers will not want to subscribe to anything with ads in it. If your blog has huge exposure then feed management might save you some bandwidth, but generally I love getting just about all the link popularity I can get.