When considering multiple income streams you have to think, Are they a good fit for your business and also will they be effective to drive in income from multiple sources? but I would research them and work on a few methods of multiple income, because they can make your business more stable in the long run by providing other earning opportunities from your website that all combine together for maximum income potential.
One of the most easiest income streams to set up is CPA affiliate offers and these typically are ones that when you get leads to do something for the merchant such as sign up or provide their email address and you get paid per lead or as the saying goes Cost Per Aquisition.
So really though they are that important and it is best to build up many income streams, what I'm doing is building up advertising revenue and then combining it with affiliate marketing from Amazon Associates and the Ebay Partner Network which are both affiliate programs that are two separate income streams and then I promote relevant but good quality affiliate products and services in many different niches to build up yet more passive income.
Also setting up your own products is another way of positioning yourself as an expert, but also an income stream that will grow in time, many do ebooks or free ebooks or reports or membership sites which pay everytime a member signs up to the paid subscription.
So if you have websites or blogs online, it is worth trying to earn multiple income streams from your online efforts, as this is better for you, in a finacial sense, and the more you think of income coming from different sources, then the better placed you are to do this and engrain it on your mind.