Firstly, because your list belongs to you once you've built it. It gives you security. Regardless of what changes the search engines make to their algorithms, you'll always have a source of really targeted traffic.

Secondly, having your own subscriber list gives you the opportunity to expose your visitors to your offers multiple times. Very few visitors will buy from you on their first visit to your site, so the more times you can advertise to them, the higher your chances of making a sale.

Basically the larger your list the more you'll make over a longer period of time.

Having your own large list of subscribers also gives you a competitive advantage over would be competitors. Having a list means you can pull in free traffic anytime you want with a simple email. This means you have a significant advantage over new marketers entering your niche. Visitors will therefore cost you less than your competition and this competitive advantage will make it harder for new entrants to establish themselves.

All online marketers should make list building a priority if they're serious about making money online. It gives you the foundation for longer term success. With a targeted list your sales should increase as you repeatedly pitch to targeted contacts.

Well written, regular emails should yield regular sales and profits, the majority of which wouldn't have happened without a list. Your list allows you to convert visitors who weren't going to make a purchase into sales. The vast majority of your visitors will find your site once and never come back, that is unless you can entice them to subscribe to your list. Most webmasters concentrate on generating new traffic and not on building their list which is crazy! They should be concentrating on converting visitors into list members.

Another huge benefit of having your own subscriber lists is that you will find it much easier to find joint venture partners. Joint ventures can be hugely beneficial. If you partner with someone who has a huge list of their own, you can promote each others products at no extra cost, literally overnight your product can be promoted to thousands of potential buyers! The bigger your own list, the more attractive a joint venture will be to the other party.

So how do you build a huge list?

Firstly you need an opt-in box on your web pages with a compelling reason for your visitors to subscribe. A compelling reason usually takes the form of information critical to your visitors, that they can only get hold of via your opt-in box.

Secondly you need traffic. For list building you need to encourage traffic virally. Basically viral traffic is generated by your visitors telling others about your offers for you. You provide an incentive for each new subscriber to tell others. A good incentive will snowball the growth of your list.

Building a huge list will guarantee you make money online, both in the short and longer term.