Yup, I had an advertiser hawking a "Get rich at home" campaign and he targeted my site. I let it go for about 1 week but then yanked it when I realized the ads were returning about 3 cents per click. Since yanking those ads, the eCPM is slowly starting to climb back to previous levels.
I wouldn't abandon all your hard work just yet. IMO one month of bad earnings does not justify pulling AS site wide. Continue to diversify your site's potential, but from all the different posts I've seen on here, AS is still the top performer for small publishers. It certainly doesn't have to be the ONLY one. Think of your earnings for the entire year and just don't concentrate too hard on Oct.