Content networks in Adwords is a great way to get massive traffic in the fastest time, it is relatively cheaper then using the search networks. BUT they are not people who are looking for the services or products you are selling online.
I have done a major mistake of not switching off my content networks before (thank God it was once and only for a day), getting un-targeted impressions to the content networks are not really a good idea, if your PPC ads are not screaming at them to click on your ad.
That is why if I would want to use both the search and the content networks, I would separate them into two different campaigns. This way I can track and find out the type of traffic in both the networks.
Back to my past mistake of switching on the content network, is that I incur additional cost (CPC), but thank God the impressions are not taken into account in the search networks. Why?
It is because Google knows that the content network traffic are not as targeted as the search networks, so Google only take into account of impressions in the search networks.
So remember always, to switch off your content networks from your search networks. In order to get the best result for your PPC ads, thus increase in conversion.