The question here is :
[1] What's Your Objective in buying an Ads Space / Listing or PPC (Per-per-click) Advertising ?
If you are looking at getting direct response from the ads, and making a sales conversion, then think again.
The response rate is relative to a few factors:
[1] Web Traffic ( unique vistorships )
[2] Target Market / Audience
[3] Competitions
What's your expected ROI on the ads investment ?
If you are looking at Long-term Branding strategy, then go ahead.
But if you are thinking of getting good conversion rate ( in the short-term ), you might make it provided you are very good at it ... if NOT you are just throwing darts at a fast moving target.
I used to say, "When everyone trying to get in, it's time to get out !"
Having said that, you might want to go ahead and try some of these ads, and learn the experience for yourself ... that's the way to understand and grow.