On a routine visit to my doctor, she mentioned a new interactive system the organization had created for doctor/patient communication. She encouraged me to sign up, citing a few of its benefits including real-time access to recent test results, email correspondence and personal medical history. I gave it a run, and am actually pretty impressed. While I would never want it to replace valuable discussions with my physician, it's a great way to stay in touch and updated in between office visits. Other patients I have spoken to, however, fear that their personal medical information could wind up in the wrong hands and are nervous that their MDs will use the Website in lieu of a personal appointment.
My one concern would be my relationship with my PCP. Because I switched doctors when I moved to Boston, my PCP does not know me very well (and vice versa). I'd be fairly cautious of corresponding with a doctor via email who has only seen me two times. I'd much prefer the in-person interaction. That said, if you have been with the doctor for a number of years, I think it's a great way to keep in touch between routine visits.
I do think real-time access to tests results is great though. I know I get anxious waiting to hear back from the doctor's office. It's definitely the way of the future!
I think this type of a community could be really useful - worth it for the risk, in my opinion. While I agree that I would never want an online resource to completely replace routine/scheduled in-person visits, it's possible, and likely, that an effectively communicating network would reduce unnecessary visits, and therefore costs.