What are you main reasons for not using a link exchange network?

I got to say the main fear getting enough control of the automation. For example: Setting the PR built, the OBL of the backlinks, filtering out websites with bad keywords, etc

Fear of being penalized by Google.  These link networks tend to all go down at once.

I have a fear: I just tried signing up for your service, but bailed after watching the blurry product video and having lots of difficulty navigating the site. It's nearly impossible to get to the sign up form - when you scroll, the page jumps around and skips entire sections. I thought... this looks nice, I feel like I can trust these guys. That faded quickly. How could I trust your software and injecting code on my site, which is very important to me, when your site is so sloppy? The other fear, less specific to you, is how Google might make changes down the line that would penalize me. You guys just go away or change your model. For me, it could severely impact my revenue and cripple my business.