THAT practice should be illegal. One of our parents found a part-time job by keeping an eye out on snagajob.com - and one of my neighbors found a position on craigslist -- both are free for jobhunters.
But it's quite possible that MANY online websites are deceptive in the manner you depict. That's just horrible, and I wonder how common it was with the old newspaper want ads.
Newspaper want ads cost money. Online job listing in most instances do not.
If anyone is looking for a job, I personnally found these two “aggregators” to be the most helpful when I had to shut my company down and go job hunting in 2008:
http://www.simplyhired.com
http://www.indeed.com
It is true that there are numerous ads that never lead to interviews or even acknowledging receipt of your resumé. In the end, it was an industry acquaintance, a former customer actually, that led to my current employment. If you’re having difficulties finding opportunities, wrack your brain for people who might be able to help, who know you and would be willing to give you at least a fair hearing and possibly a job.