this has often been stressed by internet marketing gurus as being key to success. It seems like they're implying that about an email list. How about a list of YouTube, Twitter, or Facebook subscribers? Could any of these things be a substitute for an email list? Before, I didn't understand why having a list was important. I figured that an email was just another click through to get them on a landing page. Then I read some article which pointed out that you'll have repeat buyers / leads if they're subscribed to your list, whereas the overwhelming majority of visitors to your site wouldn't come back otherwise. That's when it made a lot of sense.
I have a question about having an e-mail list... does your address legally have to be associated with it? I've noticed when signing up for a free trial of mailchimp and a couple of others that they ask for this first. Feedburner has an option for e-mailed subscriptions which they don't make you put your address down, but I recently tested it out by signing up for my own feedburner e-mail list and it hasn't been sending emails.
Essentially, what we're talking about is that you have a distinct identity you are known by. The world associates that ID with you. Your list see that identity as what they signed up to and you trust they'll stay linked to that identity forever more, buy things from this person and so on. I've made this as clear as I can and hope it explains what you're asking...
It is not only important to have a list but also to have a relationship with that list. People want a free offer but they are also looking for good information from you. When you sign up a subscriber have a series of follow up emails giving them advice in your particular niche.
Yea having a list is very important..it's just like repeat customers at a store. It's similar to having a large social media following, although they work differently. These days you really need both if you want to really shine.