I never had much success with adsense on my web directory. In fact, I regret getting into this directory business!
It's waste of time by putting adsense on general directories, however, you can generate decent money if you put adsense on niche directories. I have a niche directories and always make $1/day by one click.
Usally only between 60-70% of submissions are approved with about 20% being spam and the other low quality, poor description etc... Real, unique visitors to date this month is 9546 - so approx 330 per day on average. Money is generated mainly from adsense and advertising, but i also get the odd featured listing submitted. I also include in the link submission email "other directories of interest" which are my own paid directories and a fair few of the free submitters from this directory go on to submit paid listings in my other directories
Spammers in the UK face a fine of up to £5,000 although not sure if anyone to date has been prosecuted successfully for it.