Well, the fact is that performances on the content network are inferior to those on the search network, especially for the ROI focused campaigns.
But, content campaigns might, and usually do, prove interesting when dealing with branding campaigns - driving qualified traffic to the site without conversion goals - or with prospect data base building actions. So this applies mostly to the B2C campaigns.
There are though rules to follow.
First that comes to mind is: never ever just activate the content network on your regular search campaigns. Building an efficient content campaign needs a separate strategy. As you are probably aware, the ads are not triggered by a single keyword in a content campaign. It's the whole ad group that defines the theme. That is why using around 10 keywords per ad group is usually enough. No need to use very specific expressions. Just put together pertinent keywords defining a specific semantic universe. And then tie them up with some relevant ad text. And then create as many ad groups as you can, following the same concept.
For B2B campaigns I would advise focusing on the site targeting. AdWords has a tool that gives you a list of sites by analyzing your own/client's, related to a keyword list that you provide or by letting you browse vertically through their proposed categories. You could identify some interesting niche sites this way. Using the classic content network as well but with a lower budget might provide you with some other sites to add to the site targeting campaign, just generate a placement report.
Nevertheless, in any case, make sure that the content campaigns are tracked correctly. When using a bid management tool this should not be a problem - usually they do all the job by themselves. But if you are only tracking the campaign with redirection URLs or with URL tags make sure you set them at the ad level and not at the keyword level as for the regular search campaigns.
Does this post make any sense?