There may be one thing companies might be willing to pay for that is specific to Dr. Dobbs. If you read that advanced article on C++ a few days ago, and you are now reading this in-depth description of scaling Linux internals, I very much would have a job for you. What other site can say the same?
Yes, this is actually one case where as a privacy conscious user, I would be ok with browsing data being used for job ad purposes. Also job ads are probably the only ones I click on. And if the ads are intra-site I don't think AdBlock would touch them (even if they do, their AdBlock detection script could say, "looking for a job? make an adblock exception for us", which is valuable data in itself). Besides, a link in the header to a job board might generate enough traffic alone.
Dr. Dobb's Jobs has a nice ring. And a freelancer board could be Dr. Dobb's Odd Jobs :)
At $300 per ad, you'd need about 800 ads a month to reach $3 mil/year. Achievable?