I will go against the crowd here, and say that Internet helps me with my faith.
You might just be speaking for them. The minority tends to be more vocal.
became an atheist by reading about religion on the Internet. He was already away from faith, since he said that he would have identified himself as religious without attending service
I disagree with your example, but not with the idea. I am not an Xian, and religion, to me, has nothing to do with service, service is just another effect.
There is a famous quote, "Power corrupts, absolute power power corrupts absolutely." That was said by someone who was denying responsibility of the individual. Power does not corrupt. Power gives corrupt people the ability to exercise their extant corruptness. A non-corrupt person would be fine with power, and we might even be the better off for it.
Similarly, the Internet does not shake anyone's faith. It stirs he whose faith has already been shaken, or just wasn't so strong to begin with. That being said, sites of...um...ill repute, will demoralize a person, and that can ultimately lead to shake his faith. But that is more an issue of morality than theism.