Well, yes and no. Sure, you can get hit with an algorithm change or penalty that destroys all your traffic. However, if you have good people who know what they are doing, this is not likely to happen, and if it does, it is easy (in most cases) to get your visits back. Panda and Penguin are another story, but if you get hit by those it is typically not accidental.
The other way visitors can access your website is by coming from other websites; in this instance, the user lands on your website after following a link from another site. The link that the user clicked on is referred to as a “backlink,” as it links back to your website. This traffic is much more beneficial to the search engine optimization (SEO) of your website as opposed to direct traffic, which has little to no effect. The reason is that Google and other search engines interpret backlinks as little doses of credibility for your website. If other credible websites are linking to your site, that must mean it is comprised of relevant and accurate content, which is exactly what search engines want.
Mobile traffic: In the Groupon experiment mentioned above, Groupon found that both browser and device matter in web analytics’ ability to track organic traffic. Although desktops using common browsers saw a smaller impact from the test (10-20 percent), mobile devices saw a 50 percent drop in direct traffic when the site was de-indexed. In short, as mobile users grow, we are likely to see direct traffic rise even more from organic search traffic.

Brankica, Very comprehensive list there. Can't think of anything else :D RT! I think the traffic sources that I hardly use is answering questions. I find that traffic conversion there is poor for me, so I don't focus too much on it. I think of all those in the list, focus on those that gives you the best kind of traffic. Forums can be a particularly useful one especially when people are there asking for help. Answering their questions and giving them a link that benefits their query is one good way of getting the right kind of traffic.
Google claims their users click (organic) search results more often than ads, essentially rebutting the research cited above. A 2012 Google study found that 81% of ad impressions and 66% of ad clicks happen when there is no associated organic search result on the first page.[2] Research has shown that searchers may have a bias against ads, unless the ads are relevant to the searcher's need or intent [3]
Understanding how people landed on your website is a key component of optimization. If you’ve ever looked at Google Analytics (and if you haven’t you should), you’ve probably seen the words “Direct,” “Referral,” and “Organic” in relation to your traffic. These are the sources where your users come from — or what Google calls channels. But what do these words really mean, and why do they matter?
What does that mean for your website? Organic Traffic is any of the customers that come to your website without clicking a link on another site (referral traffic) or clicking an ad (paid traffic) – these visitors used a known search engine and clicked a link to view your website. Much of this traffic is customers from Google, but it also includes other common search engines like Bing and Yahoo. Now that we know what it is, let’s dive into understanding how this information can help you improve your website.

The term “organic” refers to something having the characteristics of an organism. Although black hat SEO methods may boost a website’s search engine page rank in the short term, these methods could also get the site banned from the search engines altogether. However, it is more likely that readers will recognize the low quality of sites employing black hat SEO at the expense of the reader experience, which will reduce the site’s traffic and page rank over time.
Superb resource list Brankica, thank you. I've also included it this week's Erudition, not just because you're in a competition, but because it really is a resource we should all have bookmarked. Actually, I need to make it a study priority and see how many of the sources I can reasonably use on a regualr basis. Link to Erudition | Help files from Information Junkies Anonymous
Great awesome article till now its the best one I ever read for traffic generation on web and on this contest as well can be converted into an ebook too with few addons like there is a site for video starting with m cant recall the name feeling damn sleepy reading all this articles since hours,and sites like redgage and arranging giveaways depending on your site niche
Hey Jym, thanks a bunch :) Yeah, I don't think everyone need to use each and every one of these, especially at the beginning. But I do find the list useful for those with "older" blogs. When you are thinking "Where else can I go to get more people to see my blog". That is what I do with my first website. Again, I agree with the part of identifying the ones that will work the best, so we don't spend too much time getting no results. Thanks so much for the comment

For a long time, digital marketers summed up the properties of direct and organic traffic pretty similarly and simply. To most, organic traffic consists of visits from search engines, while direct traffic is made up of visits from people entering your company URL into their browser. This explanation, however, is too simplified and leaves most digital marketers short-handed when it comes to completely understanding and gaining insights from web traffic, especially organic and direct sources.