I know I have written about Dr. Google and his flaws before. Dr. Google can tell you that you have ten terminal ailments along with psoriasis, athletes foot, head lice and bed bugs when all you have is a mosquito bite. Dr. Google can be very scary. Dr. Google is not a real doctor.
There is so much medical information on line and it covers the gamut of good solid information to complete quackery and scams plus a lot of well meaning people who are sure that what worked for them will definitely work for you. You need to sort through what is there and figure out what to believe and what to ignore. My personal recommendation is to stick with the credible sites of WebMD, Mayo Clinic, BreastCancer.org, American Cancer Society, possibly your own hospital's web page etc. I would skip any website trying to sell you something that will cure you (or offers you a share in a Nigerian inheritance). Yes you can get lots of good solid information online. And an educated patient is a comfortable position to be in.
Online message boards can provide a lot of support from others coping with the same ailment and should be included in your online research. If you read to what the patients say you can learn how to cope with side effects and the ups and downs of treatment. Its not that patients are doctors and can give you advice but the general consensus you get from what everyone else is going through offers a different type of information. A group consensus can be just as helpful as online medical advice.
The New York Times published an article earlier this week on this topic. The author feels his life was saved by what he learned online. He kept reading about the same doctor for his type of cancer. He ended up going to see him a thousand miles away and felt that this doctor gave him the life saving course of treatment. (One comment on the article is that it recommends going to ACOR.org for help - that front page hasn't been updated since 2002 and it is full of broken links so I think you can skip it.)
I know I have learned a lot on line from message boards in addition to receiving (and giving I hope) a lot of support. They definitely helped balance out the ups and downs of cancer diagnosis and treatment. They also encouraged me to ask more questions of my doctors and educate myself so I was more comfortable with my course of treatments.