News Courtesy of Moz.com:
There is no doubt that Google Analytics is one of the most important tools you could use to understand your users' behavior and measure the performance of your site. There's a reason it's used by millions across the world.
But despite being such an essential part of the decision-making process for many businesses and blogs, I often find sites (of all sizes) that do little or no data filtering after installing the tracking code, which is a huge mistake.
Think of a Google Analytics property without filtered data as one of those styrofoam cakes with edible parts. It may seem genuine from the top, and it may even feel right when you cut a slice, but as you go deeper and deeper you find that much of it is artificial.
If you're one of those that haven’t properly configured their Google Analytics and you only pay attention to the summary reports, you probably won't notice that there's all sorts of bogus information mixed in with your real user data.
Ryan’s Take 
In order to accurately portray this source post from Moz I would need to snippet 4-5 times as much as I currently have. There are all KINDS of tips and advice for filtering out real traffic in Google Analytics. The author goes into great detail for dealing with spam, bots, and internal traffic. Having dealt with all of them, I can tell you that if you’re looking at raw unfiltered data, it’s going to paint a much different picture than real world visitors.
Perhaps the most egregious offender of fake traffic is bots. At least in my experience. It is not that it happens every day, but when it does, it spikes statistics and can throw your averages way out of wack. The article references an ISP by the name of OVH Hosting. If you see a bunch of new users attached to this domain, it is most likely bot traffic. In one case, I saw 50+ users from this isp in the span of a few minutes. It looks oddly suspicious when viewing the data on a daily basis. However, when viewed on a weekly or monthly timeline, it is easy to miss and makes that website’s performance look better than it actually is.
Similar to bots, spam traffic is quite the annoyance. The goal of some is to get you to click on the source of the traffic and either try to sell you something or install a malicious script. It’s not nearly as bad as it has been in the past, but the issue still persists. Filtering out bad hostnames in analytics is a good way to eliminate spam traffic in your reports. You’ll need to make a list of valid hostnames in order to do this, but the article does a good job of explaining how.
No matter how you look at it, Google Analytics is an essential tool for getting valuable user data. It’s not perfect by any means, but when combined with Webmaster Tools you can easily implement an effective SEO strategy. It allows you to discover what content is popular and who it is popular with. Whether that be real people, spam or bots, it is up to you to filter out the irrelevant data.
