* It undermines the rule of law because the government should not know what you discuss with your lawyer.
* It sabotages the health system because you should be able to talk to your doctor in privacy.
I find a more convincing argument is that the data can be abused for purposes beyond that for which it was gathered; for example, the disclosures about the DEA and 'parallel construction' shocked many people with whom I work. People respond more to the risk that their misdeeds will be discovered ( be it simple cash-in-hand tax evasion or more nefarious activities ).
Except it can leave you vulnerable to blackmail. Say your rash is a symptom of a STD which was caused by a drunken one night stand with a x/y person you met at a bar. "Now you wouldn't your partner to find out would you?" says the guy in guy in the suit...
Other ways health records can be abused if your partner or child needs a transplant and they are way down the waiting list...
* 70% of Americans are currently using some form of prescription drug. Would you be comfortable if this information was given to, say, the next employer you interview with?
* Many health issues can be embarrassing for people, even relatively benign ones. This isn't always obvious until you've experienced it.
* Mental health issues often carry a social stigma. Yet 11% of the American population currently take antidepressants.
* Health records, by necessity, include vast amounts of personal information that isn't directly medical. Addresses. Phone numbers. Social security numbers.
from CDC/NCHS Data Brief: "Antidepressant Use in Persons Aged 12 and Over: United States, 2005–2008": http://www.cdc.gov/nchs/data/databriefs/db76.htm
"Nearly 70 percent of Americans are on at least one prescription drug, and more than half take two, Mayo Clinic and Olmsted Medical Center researchers say."
from Mayo Clinic, "Nearly 7 in 10 Americans Take Prescription Drugs, Mayo Clinic, Olmsted Medical Center Find": http://www.mayoclinic.org/news2013-rst/7543.html
I would never have guessed that the number of people taking antidepressant drugs would be so high.
But who would you know if the data is abused or not if journalists can't convince their potential sources that their communication is private?
And if you - on some way - get the knowledge that your data is abused, what can you do? Sue the government? That's a lot more difficult if you can assume that the other side has potentially access to your whole strategy and to every mistake you ever did in your whole life (dirty campaigning/blackmailing).
"You wrote a letter critical of the governor. Let's see what's in your file, ..., hmm, it says here you went to LA when you told your wife you were going to SF. You wouldn't want us to tell her about that, would you?"