One criticism of banner exchange programs (such as EC and Adgitize) is that members drop by your blog only to earn click credits. I do understand this concern. But here's the way I see it:
*For a brand new (or obscure) blogger, any form of traffic is better than getting just a handful of hits a day.
*If someone visits my blog and has no incentive to stay, that's my fault--something is lacking in my content.
In other words, EC and Adgitize do a pretty decent job of bringing extra traffic to your website. But high quality content is what will keep readers there, and that is your responsibility.