So no, people aren't just frothing at the mouth when they say the money is in the list, because the single most important key to online success mailing list could very well be... list building. Having a list simply means having a mailing list of mailing list people to sell to or having a list of potential buyers. Look at it this way, if you don't have anyone to sell to, how are you going to make any money?
Some people will tell you that you don't really need to build a list to be successful. That may be true in some cases but all it means is mailing list that you have to work twice as hard. When you don't have your own mailing list, you have to be constantly searching for new people to sell to. With your own list you will have repeat customers. When your list of customers know and trust you.
Whatever products you recommend to them, they are likely to buy. It has been said many times over that it's easier to keep your old customers mailing list than to recruit new ones. Additionally the key to list building is having your own website. So if you don't, then you're not building your own list. Most likely you're building someone else's mailing list for them every time you drive traffic to their website and not yours.