I got my last full-time job through Monster. One thing I want to point out to people is that employers hate multiple applications (e. g. you apply on Monster, and then on Dice, and then on CareerBuilder, etc.). However, if employers want to stop this, they should simply only post their jobs in one location. So, it's kind of an annoying thing but you can keep your sanity if you keep extremely good notes.
As for the folks who had job offers withdrawn, etc., oy, I mean, how foolish is that???
* why did they make themselves recognizable enough to be found so easily online?
* why did they make their former employer (or the like) so easy to be recognized online?
* why did they think a potential employer wouldn't investigate them?
Sorry, but the whole thing smacks of the potential employees being dumb as fence posts, and the employers are probably more than happy to have dodged such potential bullets.
I'd never apply online. I still think the best application is one, you mail and then follow up with a phone call.