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.
Go to local events or Meetup events and connect with bloggers in your industry. An example of an event I run to connect with bloggers and people in the online marketing word is: http://www.meetup.com/Online-Marketing-Sydney/. Make friends first and then try to gain guest posts later. I am not really a fan of websites which are flooded with guest posts one after another; it is the type of thing which Google is just waiting to target.
What an awesome stuff you're sharing here, Brankica. I'm a big fan of social networking site and blogging communities. Social Sites are great way to connect other bloggers and marketers. I've great success with blog commenting. I think it's another great way to connect with blog owner and build relationship. In the earlier days of my blogging, i did commenting just to get traffic but now i do commenting to build relationship with blog owner/connect with blog owner. Anyways, Thanks for sharing this great Post. Keep Rocking. Good Luck. ~Dev
A link in the comment itself may or may not be called for. I recommend only including a link of you have a post on your site that ties in nicely. If you do, you can use it to expand your comment. “By the way, I wrote a post on this topic as well over here. My conclusions were X and they seem to contradict yours; what are your thoughts?” If you aren’t able to work in a relevant post, limit your link to in your profile for the comment, where the website field sits.
That's way easier to do when you understand what all the things you're measuring actually mean. The first place I always start when evaluating a business' marketing is figuring out where the heck all their site traffic, leads, and customers come from. But it occurred to me -- if you don't even know what all those channels mean or how they're bucketed as traffic sources to your website -- it's probably pretty hard for you to start that self-evaluation.