From Nate Silver at 538.com:
...[T]he Investors' Business Daily poll purporting to show widespread opposition to health care reform among doctors is simply not credible. There are five reasons why:
1. The survey was conducted by mail, which is unusual.
2. At least one of the questions is blatantly biased: "Do you believe the government can cover 47 million more people and it will cost less money and the quality of care will be better?"
3. ...The IBD/TIPP polling operation has literally no idea what they're doing. ... For example, I don't trust IBD/TIPP to have ... selected ... a random panel, which is harder to do than you'd think.
4. They say, somewhat ambiguously: "Responses are still coming in." ... Professional pollsters generally do not report results before the survey period is compete.
5. There is virtually no disclosure about methodology.